Apeks is owned by Aqualung and Aqualung like many other companies controls their parts sales pretty religiously. Similarly, service clinics are rare and if held require you to be shop sponsored/employed.
Scubapro has the same parts control and shop sponsored clinic attendence issues, but parts are easier to find through sources such as e-bay as they are muhc more common and much more comonly sold through grey market cources. Also Pete Wolfinger used o be Scubapro's technical guru and wrote all their tech manuals. He now operates Peterbuilt tools:
www.scubtools.com
And he sells a very good primer for reg repair:
http://www.scubatools.com/RegSavvy.html
The advantage is that the book contains many drawnings and explanations from the Scubapro tech training materials and is a good way to get to know Scubapro (as well as other) designs. He also goes into great detail on what is needed to service regulators in terms of tools, diagnosing problems, servicing, adjusting, and testing. Vance Harlow's book available through airspeed press is also a good primer for do it yourself regulator repair.
If you want simple, reliable and easy to service it is just about impossible to beat a Scubapro MK 2 R190 or MK 2 R295, especially if you pick up a few tools from Peterbuilt.
If you want a reg that is suitable for technical diving, the Mk 17 G250, MK 17 S600, or mK 17 X650 would be my first choice. The Mk 25 first stage also works very well with all of the above mentioned second stages as well, but is not as relaible in extremely cold water (below 45 degrees F). May tech divers however prefer the Mk 25's hose routing options.
An easier to service, very reliable and much less expensive alternative to the Mk 25 would be a used MK 10 or Mk 10 Plus. It offers the same general layout in terms of hose routing but has a lower parts count, is easier to service, parts are easily found used and a Mk 10 or Mk 10 Plus can be found around $100 in excellent condition. A G250 second stage can also be found used for $100-$150 and the combination will offer exceptional performance.
Alternatively, there are a couple companies that sell regs who also do not control parts sales making it fairly simple for end users to get parts to do their own maintenence. But it is hard to say how long they will continue selling parts for and supporting a particular model while both Aqualung and Scubapro have excellent records for supporting discontinued regulator models for decades, and Scubapro has a track record of improving and providing upgrades for discontinued models .
If you do go the service your own reg route, be prepared to spend $200-$300 for tools unless you already have a decent collection of hand tools, a suitably sized torque wrench, etc. If you already have adequate hand tools, you will just need $100 or so in specialty tools.
