My favorite PCP, regardless of price, are my 3 P35s. I have them in 177, 22, and 25 caliber. All are good to excellent shooters. The 25 needed a power plenum upgrade to get there. I don't know if they are out yet but a P35X or Remington Spirit X would be even better in a 25 caliber because of the 65cc plenum. That model is heavier, however. The Stoeger Bullshark is about the same as my P35s with a heavier stock and a little longer barrel. The P35s and Bullshark should be under $500, the P35X should be under $600. One reason I really like my P35s is they only weigh about 5 lbs before you attach a scope. My favorite scope for them is a Vector Veyron SFP 6-24X. That scope is under $200 at Krale (although shipping will push it a little over). Nice size for these small bullpups and surprisingly clear glass for the money.
Another SPA offering in this price range is the M60b. Krale has them just under $600 with an aluminum bottle. Air Archery Fun has them with carbon fiber bottles but they might go over $600, will be close. With a tube type air storage they would be well under $600. This gun has an externally adjustable regulator and looks a little like the FX Impact. You can get the M60 in 30 and 35 caliber.
My P35 in 22 is my most accurate P35 and possibly my most accurate PCP. It still has all it's original O-rings. I cleaned the barrel and adjusted the hammer spring a little and just shoot it. I've messed with the 177 and 25 a lot more but all have been reliable. You should expect to need to clean the barrel, adjust the trigger a little (very simple), and better balance the hammer spring to the regulator setting (although it will shoot fine without this step).
