The advice given is really good. I would also like to add that I too have never heard of regs leaking after being serviced.
I am aware of some older regulators having a slight leak at the 1st stage as part of the design to release over pressure but generally if they are new then the leak is usually the fault of the technician.
As for the part of tech diving, it's imperative that you be serious about it as it is a difficult and costly path to take, doubles band, manifolds, lift bags, reels, 3 - 6 sets of regulators etc, etc, not to mention the cost of training and effort necessary. Then there the really expensive stuff VR3s or Predators, scooters, lights, helium then there's CCRs!!!!!
Anyway, if you are set on getting a "tech" reg, these are my views:
Scubapro mk25/700A/s600. Unsealed piston design, powerful regs that keep pouring huge volumes of air at almost any depths. Difficult to make on the spot fixes without special tools.
Scubapro Mk17/700a/s600. Sealed, fairly light and fairly new design. Seems to be on par with the apeks but again, difficult to make on the spot fixes without special tools.
Apeks XTX/ATX 100 or DS4 XTS/50, tried, true and proven design in really awful conditions from cold to murky, silt laden waters with easy access to the workings of the 2nd stage should any sand particles find they way into the 2nd stage, while the 1st stage is sealed.
Doesn't quite have the power of the scubapro mk25 but more than sufficient even at extreme depths.
I have 4 apeks and thinking of getting more : )
SangP