Improving game performance with ATI cards

I have a PC game question, being somewhat of a newbie in the PC gaming arena. I play games occasionally, for example Flight Simulator X. The performance is pretty good but I was hoping for better. And I will be playing more games in the future if I can get my current box to perform better. My current specs are: Windows Vista SP0, (1) ATI X1650 Pro 512MB PCIe, Asus P5BPlus, Intel 2.6 Core 2 Conroe, 4GB Kingston DDR2 800, 2 HDDs in RAID 1.

Here's the upgrades I'm looking at:
Intel Core2 Quad Q6600 2.4Ghz (will be overclocked of course)
Intel BOXD975XBX2KR LGA 775 Intel 975X mobo (I don't like the ASUS I currently have, plus has no CrossFire support)

The part I'm not sure about and really need advice on is the video card. A friend who builds PCs has (2) ATI X1600 PCIe 256MB that he would sell me cheap. I'm considering these in a CrossFire setup, but I'm not sure if this would result in better performance.

Any advice appreciated!!

NO.....x1600 CF is not a good option......it will perform better than x1650 but not worth it nor will u see any good scaling

go for a single 4850.great value. if ur not a hardcore gamer then go with 9600GT or 8800GT or ati 3870

also u have chosen a 975 chipset mobo.thats pretty old.....go for P45/35 or x38/x48

Thanks for the advice. Here's What I've decided on:

Intel BOXDX38BT LGA 775 Intel X38 ATX mobo
Intel Core 2 Quad Q6600 Kentsfield 2.4GHz
Kingston 2GB (2 x 1GB) 240-Pin DDR3 SDRAM DDR3 1333

I'll wait on the video card until Santa comes.