Final update, I have fitted a Hardware Labs Nemesis GTX 280 at the front (following some angle grinder action). I've also plumbed the pump between the cpu and the hw labs radiator.
Now playing rss for a few hours results in gpu temps mostly in the 40's, rarely I see a 50. Playing swbf with res scaling up at 150% to really push the gpus I see 54 max. Cpu temp is always in the 50's.
Its a beauty now, quiet yet packs a punch and I'm really happy with it now knowing there's little more I can do to get any further improvement. Nevertheless, I'm now really pleased with it.
Sorted.