If you are looking for a sport bike, CBR600 f4i. reliable, forgiving, enough power to make you go...yeah I don't need to upgrade.
If you are looking for a cruiser, Shadow without a fuggin doubt!

DO NOT GET ANYTHING HIGHER THAN THE 600 Class. There is no fuggin need for anything over 600cc. You can go 170 if you need, you can accelerate faster than you will want to...anything over just shouldn't be on the street imho. Like the new ZX-14R from Kawasaki...too crazy