Upgrade help

After 2 years, I'm thinking of an upgrade. I want to keep this under $200 + a $100 newegg gift certificate ($300 total) Basically, I want to replace this:

mobo: ABIT NF7-S V2 NVIDIA nForce2 SPP chipset
CPU: AMD Athlon XP 2500+ "Barton" 333 FSB, 512k Cache
Video card: Saphire Radeon 9800 PRO 128MB, 128 Bit, 8X AGP (note that this is 128 bit)

with this:

mobo: DFI NF4 Ultra Infinity Audio/GB-LAN/IEEE-1394/PCI-E/SATA3G/DDR/ATX 64 939
CPU: AMD Athlon 64 3000+ Venice 2000MHz HT 512KB L2 Cache Socket 939
Video card: SAPPHIRE 100116 Radeon X800XL 512MB 256-bit GDDR3 VIVO PCI Express x16

and keep this:

hard drive: Maxtor Ultra 16 300GB SATA
RAM: Kingston KVR400X64C3A DDR400 PC3200 DIM 3-3-3 512*2
media drive: LITEON SOHW-812S 8X8 DVD RW Dual

I have a few questions. First is the obvious campatability issue. Second is the level of improvement that I will see. Third is the SLI thing. I have always been a Radeon guy for the vid card. Will these cards work with SLI or do I need to go to the geforce route. I somehow have it burned into my brain the the vid card I want is an excellent "bang for the buck" card. Is this true? Is there a gefore equivalent to this card that is similar in terms of price and performance? Thanks in advance.

 

I think your Budget will be alittle thinn, better look for a sale

Right now you can get 3500+ for about $10 more
http://www.newegg.com/Product/Product.asp?Item=N82E16819103533
3800+ are $139 & up
If your an OCer get an Opteron CPU, 144 er 146 I have a DFI Ultra D with an Opteron 146 she'll do 3 Ghz (stock is 2 GHz)
The 144's today are $154 & up, 146 Start around $172, the Opteron prices fluctuate alot.
Those DFI NF4 MOBO's are Power Hungry, is your PSU up to the task?
Is your's native 24 pin?
DFI recommended list:
http://www.dfi-street.com/forum/showthread.php?t=10854

They are also picky about memory they don't like value junk.
Your memory may work just fine, just an FYI
DFI NF4 recommecded memory list:
http://www.dfi-street.com/forum/showthread.php?t=24719

 

That video card does not run in "crossfire" mode. ATI use "crossfire" and Nvidia use "SLI". same thing.

Also that is a pretty weak budget for over hauling that PC. back when your 2500 barton and 9800Pro were new they were top end kit. I think no matter what you get you will see an improvement.