Audio-Technica VM750SH Dual Moving Magnet Shibata Stylus Stereo Turntable Cartridge

Your phono stage is a Musical Fidelity not a Mobile Fidelity.  It's going to be way better than the phono stage in that old Pioneer receiver, so I wouldn't even think twice about even using the internal phono stage.

IMHO, with the gear you have/are assembling, I'd look for a Shure V15TypeIII with a new SAS stylus.  Or a new Grado Black and install a new 8MZ stylus.

Both of those options would be around $200-$250.00 or so.

@mofimadness , If you have set up so many turntables you would know that Koetsu's are some of the worst tracking cartridges made. I can understand liking Lyras, Ortofons, etc. I have never used or listened to a Kiseki. Koetsu's are like Rolex watches. Rich people with very bad taste buy them which I am afraid includes me having owned a Rosewood Signature Platinum. The Ortofon Windfeld Ti is a much better cartridge. In my system only the Lyra Atlas is better than the Ti. 
As for the Shure V15, The Pioneer's tonearm is probably too heavy for it.
The AT VM750SH is a better fit for that arm. Other new cartridges to consider would be the Clearaudio moving magnet cartridges which share the same dual magnet design the ATs use. The Ortofons do better in a lighter arm. The Goldring 1042 is another excellent choice but just a bit more expensive. 

I was a Koetsu dealer for many years.  Setup a lot of them.  I don't seem to recall any severe tracking issues, but I'm getting old.  I still own several and I personally have never had an issue.  I happen to really like them.

@mijostyn doesn't like low compliance cartridges! 

jasonbourne52   

I have a Pioner PL-550 turntable with a stock tonearm.