You can satisfy a Sig sickness for $450. It's called the Sig 522. Sig saw what GSG did for the MP5 and came out with their .22LR version of the great 550!
Got the GSG-5 myself and flat love it. Can't wait to get my hands on the Sig 522.
Have to agree with the rest of the crowd. .22 is the way to go right now wtih the ammo prices. Have not shot the GSG-5, but looks cool. You might also consider a 10/22, lots of accessories available. For $450 you could build yourself a pretty neat gun.