Gents
Cheers for the replies.
The other watercooled options I was considering are the Thermaltake Water 2.0 Pro and Water 2.0 Extreme (the later rather like the H100i), and the Thermaltake New Soprano case.
I'm understand that air cooling has come a long way since 2004/5, and coolers such as the Noctua NH-14 (probably not the right name/part!) are quieter and cool slightly better, but I'm nervous about supporting over a kilo weight on the motherboard. Similarly, nervous about the traditional water cooling solutions, especially with external reservoirs! So an AIO of some description seems ideal - for me. Ok, so it looks like the Water 2.0 Pro, as that will fit at the top rear, the 'old' PSU location.
@lehtv - I currently run two rigs, one 'workstation', one gaming. I do some graphic and video work, web design, and so on. Traditionally, always bought the fastest kit I could, and a dual-cpu'er at heart (e.g DK8N and Opteron 250s, U320 SCSI RAID, ect). However, the cost/performance benefit of a dual Xeon solution doesn't work for me - money isn't a problem, I just cant justify the massive increase in expenditure (£550 for even a moderate CPU, £600 for the motherboard) for the performance gains. If my time was money, then I in terms of ROI, yes. But it isn't

Similarly, I would have built a reasonably decent game rig. Oh, I also run Exchange on a dedicated server...
I decided that an i3770K system with a 7790 would offer the best of both worlds. The CPU is powerful enough to run Photoshop, Premiere, the Matrox RT card, etc, with more than acceptable performance. Likewise, it will also run the games I play (AvP, mechwarrior, CoD). Thus, the opportunity to use one box for both. With a dual booting system, using two SSDs (Samsung 840s), one for booting into a work OS and one into the game OS, I can do this without worrying too much about cluttering the work system with games.
I may still build a games rig based on a G1 Sniper 3, i5, and swap the 7790 into that and a 7750 into the i7. I have 3 x 27" monitors, to experiment with a dual LCD work screen, or maybe even a triple headed display (if the 7790 or 7750 will do that, thats for me to play with!) - something I've not done since the days of Parhelia.
Why the Asus? Flexibillity. If gaming performance is acceptable to me, I saved £100 or so over the Sniper. It will sure be ok as a work platform compared to the Tyan 2895! Not as great as a socket 2011 solution, but about £1000 cheaper in the end. I get a good 'bang for my buck'. And I got a good deal on the board, CPU, and RAM from Amazon. Just waiting on delivery! Then its case, PSU, drives.. and a morning installing Win7 and updates! Typical, I moved from a house with 80Mb/20Mb to 8Mb/440Kb
Thanks for the tip on the PSU, again, if I need/decide to build a dedicated game box, then I already have some parts I can migrate over

(most of the parts in my boxes cascade down when I upgrade one component or another).
Comments appreciated folks, as are further thoughts - many thanks!
Forgot to add, I'm also looking at moving the Exchange box to a VM on the new work rig. Maybe. I might just migrate to cloud... But its the flexibillity thing again.