If the OP is set on a gun with louder report, I guess a .22LR is out of the question... I bought my little beater Ruger Std. for $140 a couple years back because for the difference in price between ten $18 boxes of 50 rounds, and one $20 box of 500 rounds, I could recoup the price by the time I'd shot 500 rounds - which was a really inexpensive way to pick up a lot of practice.
Jus' sayin'...
Also, I'd jump on the band wagon of trying out guns before buying. I shot my friend John's Ruger, and liked it a whole lot; it just flat out fit. So when I found one in a gun store, I knew I'd like it.
I didn't do that when I bought my G21, but I got it cheap enough that I could just flip it if I didn't like it. I didn't really like shooting my buddy's G19, and thought I was going to just sell for a modest profit. I liked the gun, and made it my EDC piece. Go figure.
But, I wouldn't recommend a person spending $$$ on a gun that he isn't sure he's gonna' like, unless he can get his cash (and maybe more) back out real quick and easy.
As far as other non-.22LR guns go, how 'bout a wheelgun chambered in .357? Gives the opportunity to shoot .38 also. $600 will buy a guy a pretty darn nice revolver if he shops around!
One other thing... I haven't shot any guns chambered in 7.62 X 25; it's supposed to be a zesty little round with a snappy report and cool looking fireball - a fun thing to shoot. (not that I'd necessarily recommend a guy pick up a gun chambered in a slightly oddball caliber as a first piece, but heck, my first pistol purchased was chambered in Makarov).
Anybody have any experience with this? This might be another thing for the OP to look into.
-Bill