Will this HS fit this MB?

[Slaymate]

It's only a little bigger than my true so it should fit either vertically or horizontal. Your main problem would be with a dual fan setup, but I think it would still fit if your case is big enough. Another problem can arise if your using ram with tall heatsinks on them.

You can see in this picture that my True (which is about 10mm thinner than the prolimatech) with a 38mm fan requires me to use the 2nd, 4th and 6th memory slots. So you'll have to use a regular 25mm fan and the 2nd, 4th and 6th slots. If you get ram with bigger heatsinks you may have to raise the fan so it misses them and then the fan won't cover the whole heatsink.

Also notice the extra fans I added

The Prolimatech is cheaper here
Prolimatech Megahalem for Intel Socket 775 /1366 Products Model: MEGAHALEM [MEGAHALEM] : Performance-PCs.com, ... sleeve it and they will come

I have one of these on my workstation. It's adjustable from quiet to loud (110 cfm). It should work nicely and it's Blue
Cooler Master Y720DCD-25T1-GP 120mm Blue LED Silent Fan 110CFM 16dBA - Sleeved Products Model: Y720DCD-25T1-GP [Y720DCD-25T1-GP] : Performance-PCs.com, ... sleeve it and they will come

Here's the fan I'm using on my True Copper (I painted mine), it may fit if your lucky.
SCYTHE "ULTRA KAZE" 120 x 38 mm 3000 rpm Quiet Case Fan - High Speed - Sleeved Products Model: DFS123812H-3000 [DFS123812H-3000] : Performance-PCs.com, ... sleeve it and they will come

 

[Guttzu]

It's only a little bigger than my true so it should fit either vertically or horizontal. Your main problem would be with a dual fan setup, but I think it would still fit if your case is big enough. Another problem can arise if your using ram with tall heatsinks on them.

You can see in this picture that my True (which is about 10mm thinner than the prolimatech) with a 38mm fan requires me to use the 2nd, 4th and 6th memory slots. So you'll have to use a regular 25mm fan and the 2nd, 4th and 6th slots. If you get ram with bigger heatsinks you may have to raise the fan so it misses them and then the fan won't cover the whole heatsink.

Also notice the extra fans I added

The Prolimatech is cheaper here
Prolimatech Megahalem for Intel Socket 775 /1366 Products Model: MEGAHALEM [MEGAHALEM] : Performance-PCs.com, ... sleeve it and they will come

I have one of these on my workstation. It's adjustable from quiet to loud (110 cfm). It should work nicely and it's Blue
Cooler Master Y720DCD-25T1-GP 120mm Blue LED Silent Fan 110CFM 16dBA - Sleeved Products Model: Y720DCD-25T1-GP [Y720DCD-25T1-GP] : Performance-PCs.com, ... sleeve it and they will come

Here's the fan I'm using on my True Copper (I painted mine), it may fit if your lucky.
SCYTHE "ULTRA KAZE" 120 x 38 mm 3000 rpm Quiet Case Fan - High Speed - Sleeved Products Model: DFS123812H-3000 [DFS123812H-3000] : Performance-PCs.com, ... sleeve it and they will come

Thanks for the great advice man! I think I'll go with the Cooler Master one cause I want to go with 2 blue LED 120's mounted behind the HDD cage.... should look cool in the Cooler Master 840 ATCS with the windowed side panel.... what fans would yall recommend to mount on the HDD cage? Room for 2 and I guess they really don't need to be blue but it would be cool if they were...

Edit: What about these for the HDD cage.....Newegg.com - COOLER MASTER R4-L2S-122B-GP 120mm 4 BLUE LED LED Case Fan - Case Fans

 

[S0ULphIRE]

I've heard some good things about the Noctua nh-u12p se1366. Apparently it's just as good and, in some scenarios, even better then the TRUE. anyone used it?

 

[Slaymate]

I've seen some rigs that use the Noctua. It performs pretty good, but I would classify it below the True and Prolimatech. But overall, it's the user that has to properly configure his system to take advantage of any heatsink.

 

[S0ULphIRE]

Well I reckon I'm giving it a shot, I'll let you know how it turns out...

 

[Guttzu]

I'm ordering the Prolimatech Megahalem for Intel Socket 775 /1366 Products Model: MEGAHALEM [MEGAHALEM] : Performance-PCs.com, ... sleeve it and they will come tomorrow so I need to figure out an amazing fan to put on it... I know Slaymate suggested the Cooler Master Y720DCD-25T1-GP 120mm Blue LED Silent Fan 110CFM 16dBA - Sleeved Products Model: Y720DCD-25T1-GP [Y720DCD-25T1-GP] : Performance-PCs.com, ... sleeve it and they will come but is that really the best fan that will fit it? I have the Cooler Master ATCS 840 case so there is plenty of room... the thing is huge... I just want to get the best fan possible for it... doesn't matter to me if it is LED or Not...

 

[Slaymate]

If it will fit go with this

SCYTHE "ULTRA KAZE" 120 x 38 mm 3000 rpm Quiet Case Fan - High Speed - Sleeved Products Model: DFS123812H-3000 [DFS123812H-3000] : Performance-PCs.com, ... sleeve it and they will come

 

[Guttzu]

If it will fit go with this

SCYTHE "ULTRA KAZE" 120 x 38 mm 3000 rpm Quiet Case Fan - High Speed - Sleeved Products Model: DFS123812H-3000 [DFS123812H-3000] : Performance-PCs.com, ... sleeve it and they will come

I don't plan on doing insane OC'n so what would be the best 120mm fan that would for sure fit? I mean I can always put the Ultra Kaze on there later if I want to do crazy OC'n but for now I just want the best fan that will for sure fit my case... thanks in advance for help!

Edit:

I went ahead and ordered the Ultra Kaze 120x38mm 3000 so hopefully it will fit!!!