Based on what you've stated, I believe Taipan Veteran .25 cal Long is the ticket:
* Trouble-free
* Powerful
* Externally accessible regulator ---> easy adjustability
* Quiet, relatively speaking
* Excellent accuracy
* LW barrel pushes the 34.7 VK slugs well ---> very good accuracy
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I've never owned an EDgun. Those who do own them swear by them. I do intend to try the EDgun Matador R5m in .177 caliber soon.
Addendum: Included in the photo I posted above is an FX Wildcat MK1 .25 cal -- my first bullpup. Now that bullpup sets the bar high for the genre.
The WC is supremely accurate, lightweight (lighter than the Vet), ergonomic and aesthetically appealing. My Wildcat Mk2 .30 cal comes with the externally accessable regulator also. However, I had to adjust the hammer spring -- which was Loctited -- to get the desired tune.
Finally, the Taipan Veteran will not double-load pellets, while the WC does. A minor inconvenience, however.