Thanks for the answers so far peeps, keep 'em coming
Preatoris - I thought it was about time to consider AMD as well as Intel since I've only ever used Intel even though they've not been totally reliable in their policies and practices.
Bomb Bloke - sadly the case used byDell is a total pain in the rear and does not allow the cooling I wanted to put in it. Furthermore the small amount of upgrading I've done on it to date means the machine is woefully underpowered and how I manage to keep it running at times is beyond my ken. There isn't a more powerful Dell PSU available for this box hence my consideration of an Own Build.
Crazy Gringo - great info. I'm not sure about going down the SLI route for graphics because I don't think I use the machine eneough for games requiring that kind of grunt. This machine has a 6800GT in it since the start of the year and I've been quite impressed. For the new box I'm considering a 7900GT. I use Adobe apps and RAM is a must so I'm aiming at 2GB to start with. The HDD will be 200GB with room for a slave.
Current games in play are Far Cry, Fallout Tactics BoS, Civ4, Hearts fo Iron II, Empire Earth II, both Divine Divinities, and online Realms of Mayhem and Urban Dead. Core apps for me outside of gaming - Adobe Photoshop CS2, MS Publisher, Macromedia Studio (just installed), Extensis Studio suite.
This biggest annoyance about my current PC is how poor it is for upgrading althogh it is well up to spec for most bits I mess about with.
Peeps one thing I am leery about and that's the apparent fact most mothercards come with on board sound. Just how reliable is it when it comes to gaming?