600hp should work on the stock bottom end. Start approaching 700 and you'll probably want to start looking at forged internals and other major upgrades. You can technically do that at 600 just to be safe if you want to spend the money.
LSA if you want good power that has a lot of available replacement parts and knowledge from people, and you don't want to spend a lot. Doesn't need a hood change like you heard, it'll just make a small indentation in the fire blanket, no worries.
Whipple, Harrop, or Magnuson if you want more power-capability than that and still have a roots-style blower.
Procharger if you want something that builds power more like a turbo-setup than the others listed above.
Custom turbo for massive power, but you'll need a loooot of other expensive upgrades if you are reaching for high power levels. This isn't necessary if you're only doing the 600hp like you said.
I have an LSA since I wasn't chasing high numbers and just wanted a nice, reliable setup that I could easily find parts if they break. Plus it looks factory on this car (should have come with an LSA option from the start honestly, but I understand the logistics to do that wouldn't make much sense). I would have done Procharger if I wanted more power. But I got my entire build bought, installed, tuned, and shipped all for only a little bit more than just buying the other superchargers, and that was all I needed. Around $9k total for everything involved and couldn't be happier!
You can view my build here, but looks like you will be chasing higher numbers than me:
smann's LSA Build!