LS integra. That's some pretty dumb advice. Especially the 750 part. Which if you are bored with the power of a 600 you need to try taking a turn which is where the real fun begins. Hell nothing beats the feeling of passing some joker on a new GSXR1000 with 18" chicken strips in the mountains on my 78rwhp 1996 CBR600 F3.

My very first bike was a 1994 Yamaha XJ600 (SecaII) that I got in great shape for $1500. It was a 600cc air cooled inline 4. Which is nowhere near as powerful as an inline 4 Race Replica. But I couldn't think of a better bike to start on. It didn't have to scream in the RPMs to cruise the interstate. It had decent midrange to let you scoot when you needed too. It sounded cool as hell (Despite it wasn't going anywhere fast).

Here is some video of me racing a 03 stock 350z. As you can see nothing super fast but a great learner bike. You could cruise at 70mph at a comfortable RPM and I have gotten it to a Spedo 135mph (Which was probably a true 120mph). Now this video was from my squid days.
http://www.youtube.com/watch?v=t1VCVN4UZ30
It was nimble and very comfortable.

Now if you can get a used Ninja250 for $1000 or so. You could ride that for a few months to get some experience in (And make sure you really do want a motorcycle) and save up some cash. Once you get the basics down you could move up to a SV650 and ride that for the rest of your life and never get bored.