Hi all!

If anyone has the time or inclination, I was looking for advice and criticism over an upgrade to my older PC.

I am finishing Uni in a few months and I am looking to get my second PC up to scratch as a media PC/backup gaming rig. It is a Dell Dimension 8400 about 3 years old and has following specs:
Dell Case
Dell 350W Power Supply
Dell 925X Motherboard
Pentium 4 530 (3.0GHz), stock Dell Cooler
4GB GeIL PC2-5300 (Added upgrade)
1x 160GB HD, 1x 80GB HD
ATI Radeon X800XT PCI-Express 256MB
DVD+RW Drive

Now, I'm really looking to replace the Case, Power Supply, Motherboard (all proprietary Dell stuff), and probably processor. If budget runs to it, a current mid-range Nvidia Graphics card for easier HD viewing and gaming would be handy.

CASE: (incl. power supply to keep budget down) that looks reasonably smart, doesn't have to be super small (I was thinking something like this Scan Case) or maybe push the boat out for this?

MOTHERBOARD: this is probably where I need the most help...! I was on top of things a while back when I bought my main PC (Asus P5B Deluxe 965 Chipset Mobo) but I'm not sure what the chipset to aim for is now. Is P35 the mainstream choice? Looking to get a new Core 2 Duo and probably try and stick with Asus as I'm familiar. Looking at £60-70 mark? Maybe this?

CPU: Thinking this is a worthwhile upgrade over my existing P4 530, as heat and power draw are currently so high! Core 2 Duo (no need for quad core in second PC) so was think either E8300
or E8400 as seen here.. The alternative here is that I buy a new QuadCore for my main PC (currently running C2D 6600@3.0GHz) and swap out the C2D to the Dell. That would mean undoing all the factory done Overclocking (its a 3XS from Scan) which is a bit daunting.

Graphics: Probably would look at a £115ish 8800GT or up to GTS, as it may well be attached to a Full HDTV. Would an ATI be better at the mo, considering I'm thinking about Mid-Range?

Anyway, all that puts my budget at ~£220-250 without graphics but with the odd extra accessory in there so, what do you think? Any and all comments welcome!