I don't see any problem with that goal on an LS7. I do know that a lot of guys are saying that the stock intake manifold is about done at that level. It just won't flow enough, it needs help at that point.
I went with a baby cam, springs, retainers, 1 7/8" headers, and a tune. According to Katech, the numbers they are getting with the same combo, it should make just over 600hp at the crank. I chassis dyno'd my car when it was brand new, and with only 19* total timing, it made 500rwhp. I'm running 26* now, and I should have it on the chassis dyno Friday evening so I'll have updated numbers.
Anyways, I don't see your goal as a problem. Should be easily attainable. There are many, many real world results
HERE.
I should add for the sake of discussion that Kurt had an LS7 that was identical to mine - a bone stock LS7 except for the same baby Katech cam, springs, retainers... It was exactly the same combo as mine - except it had a Kinsler IR intake - and it made 666hp on an engine dyno.