That is a beastly build for sure. Too much GPU and too little GPU for a balanced build.
You can drop the AS5 thermal compound. The AC Freezer7 Pro has excellent thermal compound (AC MX-2) pre-applied and in the right amount and pattern for install.
I think you use that poundage saved to get a 2nd case fan for the Tsunami.
If you need to trim about £36 quid or a smidge more: Triple Core Athlon II X3 450 3.2GHz £60
The Athlon II X3 450 and Radeon HD 6850 will be a really well balanced gaming rig. And still Beastly for excellent gaming IMO.
Here is what I'm thinking now.
A new HD 5770 and a decent PSU if needed....
If you're not happy with the upgraded performance you can STILL move on with your upgrade plan moving the video card and PSU into the new system.
The AM3 motherboard you're thinking about won't take the future AMD processors due out later this year. It's what some would call a 'dead socket' since there is no future upgrade path.
If the new video card and power supply can tide you over till the new Bulldozer/LLano parts are available later this year... or the new Sandy Bridge CPUs/MBs go back on sale.... you'll have just a whole lot more future upgrade options.