Not sure about that, Chris. I went straight from an 05 to an 07 and the extra 37 bhp is very noticeable. The engine is smoother and revs out far more freely, making a delicious noise at the top end. The power is right through the range and there's no perceptible loss of torque low down. When you factor in the newer car, warranty, interior tweeks etc and consider the time, trouble, effort and mods required to get a remap to that level IMHO it makes more sense to pay the extra for an 07. In fact Roast's car looks pretty good value to me at £17.5 with a Nismo kit, wheels etc.
I suppose its worth bearing in mind that if you want to make more major engine mods there's less around for the HR engine.