basically the LS2 is the same as the LS6 except the displacement. a lot of stuff from the LS6 was carried over directly to the LS2 like the famous 243 casting heads.
honestly if you want the most bang for your buck and are spending some coin then you want to go to the new rectangular port stuff and stay away from the cathedral port stuff. An L92, L76, LY6(I think, I'd have to double check) LS3 will get you into a 6.0L (LY6) or 6.2L displacement. the 4.0" bore on the 6.0L and bigger allows you to run the rectangular port heads and intake and they also have bigger valves that cant run on the smaller bores. if you buy anything smaller than a 6.0" displacement with a 4.000" bore you are pretty much handcuffing yourself for "cheap" big HP add ons. L92 heads are less than 700/pr, add a cam and tuning and you have 500hp.
I have a 6.2L L92 with the car (L76) intake and it has cam phasing and I'll run cam from mast motorsports and it should be good for 480 ft-lbs and 530 hp in pretty much stock trim except a cam and tuning.