NEW build advice- Gaming PC to play GTA 4 for $650?

[diw321]

APPROXIMATE PURCHASE DATE: Soon if the hardware is right, but will wait if something REMARKABLY better is 'just around the corner'
BUDGET RANGE: $550-650 After Rebates

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: GTA 4 & Crysis gaming, 24 hour powered on, HD movies, web browsing

PARTS NOT REQUIRED:Keyboard, Mouse, 22" Viewsonic 1680*1050 Monitor, Speakers, 1 TB WD HDD, Old IDE DVD RW, 580W Mushkin HP580-AP Power Supply, Win 7 Ultimate, Office 2007

PREFERRED WEBSITE(S) FOR PARTS: newegg.com, Tigerdirect.com, amazon.com, FRYS (local or frys.com)

COUNTRY OF ORIGIN: US

PARTS PREFERENCES: Core i5, SLI motherboard (EVGA, Gigabyte, MSI, Intel), 4 GB DDR3

OVERCLOCKING: Maybe

SLI OR CROSSFIRE: Maybe (If 580w is enough)

MONITOR RESOLUTION: 1680*1050

ADDITIONAL COMMENTS: As far as new components, I am looking at two combos newegg has for sale.
This one:
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.280597&nm_mc=EMC-IGNEFL110509&cm_mmc=EMC-IGNEFL110509-_-Combo-_-LM5A-_-Combo280597
$386.97 after Mail-in
and:

http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.291132
$496.96 after Mail-in rebate

Obviously with the first one I would have to get a Video Card but the 9800 GTX is the main reason the second combo is more expensive.
This is around what I would like to spend, with the whole build not being higher then ~$650. Is the 9800GTX good enough for GTA 4? I know how it loves to eat video memory and power (If i dropped in two for SLI). If I get the first combo, I am leaning towards the GTX 285 or the ATi 5750 but beyond that I would have to get a new power supply, which I just bought. Also, is the DDR3 Ram included in these combos good? all the OCZ products I have know work great (flash drive, DDR2) but what about this?

 

[sonic-boom]

A i5 build on this budget is really pushing, that 9800GTX is really outdated, would need to downgrade processor and up the video to get a balanced system @ 650.

 

[dndhatcher]

The Mushkin 580 has two 6pin PCIE cables and should be able to power a 5870, 5850 or two 5770s. Not sure which GPUs want an 8pin PCIE cable, but none of the new 5000s need it.

GTA4 does use the quad core CPU well so you might get away with a 5770 at 1680x10505 with an i5. For your budget, though going athlon IIx4 and 5850 might make more sense.
GTA Benchmarks for new ATI cards:
http://www.tomshardware.com/reviews/radeon-hd-5770,2446-13.html