I wouldn't go CO2 over SSP. If you can manage the charging then there are better pistols but really I'd go for PCP. As has been said get to a club and try and get a feel for some of the likely contenders, Steyr, Walther, Morini, FWB etc. They will all shoot as good as each other but some will feel better to you. At the end of the day the top pistols allow a greater degree of fit so it's really getting the grip size right off the bat so you don't need to buy another unnecessarily.

You won't lose much if anything on a good quality SH PCP, but you will save a fortune on buying brand new. I've had a few 10m match pistols but if I were going to buy another (I have arguably the best already with a Steyr Evo10e) I'd go to a shop and get the fit right. For me I have a Walther with a M grip which fits like a glove but my Steyr was L and now I have a Rink on it, also L. So If I were going to spend the best part of 2k again on a Walther LP500 I'd want to try it with a L grip just to make sure. The rest of the pistols bits are all broadly similar. I do like that Steyr have easy to adjust sights making corrections on the fly dead easy, but the Walther needs adjusting with an allen key which is no great shakes either really. Silly little things like that are the things I look at now. One or two cylinders, never had an issue with a Walther cylinder but they only usually supply one where as Steyr do two. I needed the extra one once as I had a failure with the other holding the charge.