i would suggest getting the 2400+ it is only 200mhz less than a barton 2800+, and by the way if you do decide to go for a barton 2800+ ive got an extra i can sell you with heatsink and all, ill even give you a much nicer after-market heatsink with it... but even though i stand to gain from selling you 2800+ im telling you to go 2400+ cause once you read up on overclocking you will want to do it, and be stuck with a chip that is not the best overclocker... just my opinion but if you get into overclocking you will kick yourself later, and 2400+ doesnt have very bad performance at all.
EDIT: ive looked for a cheaper xp-m2400+ and if you're not averse to using ebay there is an item on there that has 2 days left but is only at 19 dollars, being as newegg price on it has jumped(i got it for 83 shipped).
here's the link(if this is illegal then a mod can just remove it, im not trying to break rules just help someone out)
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=44935&item=6722565233&rd=1&ssPageName=WDVW
EDIT: ive looked for a cheaper xp-m2400+ and if you're not averse to using ebay there is an item on there that has 2 days left but is only at 19 dollars, being as newegg price on it has jumped(i got it for 83 shipped).
here's the link(if this is illegal then a mod can just remove it, im not trying to break rules just help someone out)
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=44935&item=6722565233&rd=1&ssPageName=WDVW