What cartridge for MMF-7?

Your selection of phono stage will have alot to do with what cartridge you can use. You need to have the proper amount of gain for the cartridge. I think that if you are going to use a low cost phono stage, that you would be better with a good quality MM cartridge. Possibly the Goldring 1042. Another possibility would be the high output MC like the Eroica or a Dynavector 10x4. But remember the phono stage is an important part of the analog system, and should not be skimped on. Reduced performance of a phono stage will lower the performance of your whole analog rig.

Stuart, thanks. Yes I recommended MM becuase of the output. With low output MC, there is more gain needed, and inexpensive phono stages aren't known for doing that very well.

Here's what I'd recommend. Go the inexpensive route on the phono stage and the cartridge, with the idea of upgrading both when you can. A rule that I generally go by is to never spend more on your cartridge than on your table. If the cartridge costs more than your table, you can get better sound by upgrading the table, than upgrading the cartridge. The Goldring MM cartridges are surprisingly good for the money. If you want a good low priced phono stage, take a look at the Gram Slee line. They have a good one that will do MM for low bucks, and it sounds good. Also you might check out the Hagerman Bugle for $125.

About your frequency response hump at 40-50Hz, that is probably a room interaction. It may depend on where you are standing when you take the measurement. It may be quite different in different spots in the room. If you are doing it at your chair, you may even consider a change in chair position, or a change in speaker position. Sometimes getting the speakers off the floor onto a low stand with an open front can smooth out a bass hump a little. It may even be inherent in your speakers. That is not unusual.

Sure you could do that on the Project 9. Try a Denon Dl103R or a Ortofon X5-MC. An EAR 834P is a good tube phono stage at a reasonable price.