I picked up the MK5 conversion kit from rockstartpaintball.com. I love it. The build quality is solid at least on new ones. All of the pieces including the ones from my stock A5 fit perfectly.
Personal preference but if you get the MKV kit, also get the ego grip piece that they sell. It goes between the magwell and the trigger frame and makes it look much better.
After DMAG magwell:
Not only are DMAGs cheaper, but I think they look better two. Sure you have to flip half way through the mag, but its easy to do one handed.