FWIW I bought a HiCap in 9x18, with 1 extra Promag mag, extra Pearce grip, box, paperwork and cleaning rod for $175.00 and think I got a deal. So if it's anywhere near that price, I'd jump on it.
Also Makarov.com says that original Russian mags can fetch $50.00 each so consider that in the deal.
8 round mags will work in the HiCaps.
I haven't tried mine yet but have heard the Promags are poor but you may get lucky. Makarov.com has 10rd mags for $28.00. Check their site out. There is a lot of information there and parts and accessories.