best cartridge for MMF-7, stock tonearm,below1000

I'm not sure if the shelter would be a good match on the Pro-ject arm, not enough effective mass with a cartridge that has fairly low compliance. Not sure about the other two that you mention. Here's one suggestion, there is a guy over on the Asylum that is using a Benz Glider on his MMF 7 and seems happy with it. You do need to be careful with cartridge selection, think high compliance to be safe. I owned a MMF7 for a few years and while it is a great table for the money it may not be up to enabling every cartridge to do its best. I'd be afraid that you may be disappointed after spending alot of money, just a word of caution. I used a V15VxMR and was happy with it on that table.

I also would be cautious about spending more than $250 for a cartridge on a MMF7. I have never heard much praise for that arm or table.

What a waste of time!
If you really have money to spend, then the order of spending in vinyl that'll get you to a much higher plane is turntable, tonearm & lastly cartridge. Don't waste your money on a new cart. when the factory supplied Eroica is good enough. Hope that you selected the Eroica low output. This TT is not resolving enough to warrant the use of one of the next tier cartridges. The improvement will be marginal & the ROI low.
Called a spade, a spade----but it's not a personal attack! I hope that you'll take it in the right spirit. FWIW. IMO.

Thanks, I know the table and arm combo is not the greatest, but my stylus needs replaced and I figured it would be a good time to spend the money on one I could carry over to a different TT. I have the MMF-7 in a different room than my speakers, it feels no sound. Would a different arm be a worthy investment? I have a RB250 in my closet, will it work on the MMF deck? Also,Bombaywalla
you stated that with the next tier carts the ROI will be low, could you explain what that means? thanks for your help, Rob

If you wanted to stay under $1000, the best play might be to sell your entire rig, add $1000, and buy a new (used) rig. for $1500-2000 you can get a very good deck - I've seen LP12, Scout, various Sota and VPI HW, Nottingham, etc in that range - all better basic decks than the Music Hall/Pro-ject. Heck, I recently got an Oracle/Koetsu for that.