Need advice on a good Phono preamp

I currently have a Music hall 5 with upgraded kimber wires .
It has a new Benz Micro Gold Low output moving coil cartridge.

I have currently a low cost opera audio PPM-6 Phono preamp.
I get a low hum in the speakers and it does not seem to do the job.

I can sell it for a loss to move it and can invest up to 700.00 US for a used phono that works well with a low output MC .5MV....

Or should I just sell the cartrige and buy another MM or High output MC???

I used a PS audio PCA2 preamp and a Halo A-21 Parasound paired with Revel Preforma 30's. I listen to rock and jazz.

I use good Nordost and cardas cables.

Thanks in advance for any info......

I have a Lehmann "Black Cube" that is fantastic. It is a VERY detailed phono pre and fits exactly in your $700 budget. It also has adjustable loading for MC and an input for MM. It may also be upgraded down the road. I used it with a LYRA Argo-i cartridge and a VPI Scoutmaster.
I have been extremely happy with a Heed Quasar that I got as a demo for $750. It works great with a .3mv Dynavector.
The Nova Phonomena uses rechargeable batteries D/C(it charges them itself) eliminating line hums etc. and can be run A/C if you want. It is also very adjustable affording a wide choice of cartridges. There is one at auction on AgoN presently that should be in your $ range.
Look at the Marchand in kit form or built which is said to be great. Also, the EAR 834 is a classic, but MC may be an issue. jallen