just stay with 4400, it's essentially the same chip as the 4800 clocked down. However, the 4600 is a manchester with a smaller cache than the toledo cores, so I'd go with 4400 over 4600 for cache, and 4400 over the 4800 for price.
I'd suggest OCZ (perhaps the dual platninum- aroudn that price range with mail-in rebate)memory but if not, corsair XMS over those patriot.
That 7900gtx is not liekly to go down significantly soon considering the demand is huge and the it's out of stock everywhere.
Might want to look at sapphire x1900xt's which are in stock and cheaper. If moving to ATI is too big a leap for you, then go with 7900gt