I have a chance to get a low use SRM pro with SRAM cranks and PC V. I've seen the SRM's on the road but never ridden or actually messed with one in person.
Also, I ride 175mm's typically, the SRM is 172.5mm. I know only 2.5mm, but is there a way to swap spiders from the 172.5's to my current 175's?
1) The wired SRM with PCV is a great combination. The display gives you everything you want in one neat package and even the interval mode is well thought out. It's very easy to use.
2) You can slope / calibrate them at home. Directions on the web. You can also do your own battery swaps on the crank if you want to. There was just a nice thread on this in WW.
3) If you can buy one used at a good price why not get it, try it, and if you like it keep it and if not just resell? It won't take you long to decide if you like it better than the Quark setup.
4) Don't know about the spiders but just write SRM in Boulder. They are really good about responding to email and supporting the product.