new system - PSU, Mobo questions (SLI or not?)

[mikeshotgun]

Hi guys - looking to build a new system on a budget under £600. I've built a few times before, but haven't been in the game since 2006. I'm pretty much settled on a Q6600 with a 9800GTX.


Couple of questions:

1. I like the look of the Corsair 650W TX for my PSU, if this is a bad choice, please let me know - I'm quite behind on the PSU stakes but would like to stick around the £50-60 mark on this.

2. I'm not keen to drop any money on a new case - I've got an Antec P180 from my last venture and that's serving me pretty well. That said, is there any compelling reason to get a new case, or can I stick with this one?

3. Big one - what motherboard do I get?

My thoughts are -

I'm running 1440 x 900 on my 19 inch, but will probably upgrade to 24 inch when I've got the funds, so will I be needing SLI up on this in the future, or is the single card sufficient?

I like the look of the Asus p5n32-e plus if SLI is the way forward or the p5n-d if the 700 series if preferable
Alternatively, if SLI is overrated in this context, should I go for the p45 chipset (the Asus p5q line-up speaks to my price range). Again, I've not kept up with developments in this area, so am pretty ignorant on what is best.

I've not overclocked before, but may do so this time around, so will be willing to go a bit extra for a board that allows for a performance boost.

Thanks

 

[dagger]

Sli is overrated. Nvidia chipsets are expensive and underperforms. Back when Nvidia video cards are far ahead of ATI, people would get it for sli regardless. But now, it makes no sense.

9800gtx is not the best bang for the buck. A g92 8800gts runs on identical g92 chip with 128sp, it's just clocked 25mhz lower. Performance is the same.
http://en.expreview.com/2008/04/03/geforce-9800gtx-review/12/
It cost $120 ar compared to $200.
http://fxvideocards.com/ZOTAC-GeForce-8800-GTS-G92-512MB-ZT-88SES2P-FSP-256-bit-GDDR3-PCI-Express-2.0-x16-HDCP-Ready-SLI-ZOTAC-Video-Card-p-16280.html

Or you can get x38/48 chipset motherboard for crossfire 4850s/4870s as room for upgrade. 4850 performs the same as g92 8800gts/9800gtx, and 4870 is 20% faster. P45, with pcie2.0x8 in cf mode, will bottleneck. So you need x38/48.
http://www.tweaktown.com/articles/1472/7/page_7_benchmarks_crysis/index.html

Now that the price of 3870x2 has plummeted, it's became a viable choice. The 3870x2 can still keep up with 4870 in most games. It cost $240 ar, can run up to 4 monitors if you're into that, and comes with a free game.
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121247