If Steyr and the other modern PCPs are within your budget, no problems.
If you don't want to stretch that far, how about a s/h 70s/80s world class CO2 or the Czech Aeron and Alfa.
Using 12g cartridges is cheap enough and you have good consistent shot count.
IMO pressure/velocity variations with CO2 are exaggerated, especially at 10m, offhand.
I believe the current world record of 598/600 (I think) is still held by a CO2 and may be that way for a while.
Lastly, don't overlook the Gamo Compact. It will outshoot most club level shooters, even if it doesn't cost enough!
Walther CP-2 Match, FAS 604 & Tau 7 target pistols, Smith & Wesson 6" & 4" co2 pistol, Crosman 1377,
Baikal IZH 53 pistol, Gamo CFX Royal,177, Umarex SA-10 CO2 pistol.