If it wasn't for resale, I'd have dropped an LSX block under the hood of my superformance. I've owned one LS1 and one LS3, the motor make great power with a simple cam change and tune. It has a strong power band, reliable and best of all...CHEAP. I can't imagine how much more I'd have got spending $15K on an LSX verse my pretty Roush.
http://www.youtube.com/watch?v=mY2EYgsFXf8
That LS7 sounds good on the upper end, with a cam change that would be a fire breathing monster, sad part is it made more ponies then my Roush ;(