Trying vinyl, need some help!


For the last month, I have been searching for a good cd player or transport and thought I had settled on a Mcintosh unit when I started looking and turntables. I found a Roksan Radius 5 with a Nima tonearm that was in my budget so I bought it.
Now comes the problem, the cartridge. There are so many to choose from and they are not cheap so finding one that would compliment the table/arm is a bit intimidating.
My Audio Research preamp has 2 inputs for MM, or I can purchase a dedicated MC preamp.
If anyone has any experience with the Radius 5 please let me know what you have tried.
drf24
MC cartridges beat MM and MI cartridges for sound quality and information retrieval from those vinyl grooves - contrary to what the untutored say! My experience goes back 40 years! Limited budget? Try the Denon 103R on your Pioneer - I have the same setup! 
Your sp-4 is fine. I’m sure sounds great in your system. And good for you having to know how to replace the caps and take on the soldering with the resistors. It will probably take me a month of reading and YouTube videos before I took on such a task. Really anxious to hear how your project comes out and what phono cartridge you go with. I love a good mystery!
@ roberjerman Very opinionated aren't you? I picked up the SP4 for $300, a very quick look at SP6 prices puts it in the 1500-2000 range. I wasn't really looking for advice on my preamp, I was hoping to find someone with the same or similar turntable and what cartridge they were using. The sound of a particular piece of equipment is subjective. I am only trying to wade through hundreds of choices in cartridges to hopefully get lucky and find a cartridge that mates well with the turntable and plays sweet music!
@ brianmoriarty No clue what the SP4 sounds like yet, I tested it for functionality as soon as it showed up and began tearing it down to clean and modify. Oh and I looked at the Grado Masters, I am leaning towards the Grado for now.

Thanks to all for your input, help, and opinions. It has helped narrow a large choice down to 30 to 40!