Depends on your budget largely.

Any HW, allow for a tuning kit and modifications to be made. Sad but true, things are not what they used to be and HW quality can be as good as Westlake on a bad
day (springs cut with angle grinder and not finished properly, swarf in grease in mechanism, trigger sears rougher than a badgers backside to name but a few problems, bad barrels have been known too).

Walther, never had one of their spring powered rifles but my original RM8 was woefully lacking in power.

The spring powereds I have had least problem with have been Hatsan. A 55 or 60 is a heavy gun, best in FAC admittedly (that is what it was designed for like the HW80), but still a nice rifle.