What's a phonostage, and do I need one?

A phono stage/preamp does two things: 1) provide RIAA equalization and 2) provides extra gains for the lower output of cartridges. As a general guideline, you need 30-40db extra gain over line level for high output MM cartridge, 50-60db for high output MC and over 60db for low output MC.

The phono jack of your Marantz should give you RIAA equalization and enough gain for high output MM. As long as you are using a high output MM cartridge, you don’t need to buy anything. But if you want to use a low output MM or a MC cartridge, you will need a separate phono preamp and connect its output to a line level jack, usually marked as AUX in, and not to the phono jack.

The lower priced Music Hall TTs have Goldring MM cartridges in them, and will work fine into your Marantz built-in phono stage.

In the 1970's, I had a Marantz 2270 receiver, and a Dual turntable (with Shure V15 cartridge). As Sid notes above, the phono stage in the 2270 has adequate gain to handle most moving-magnet and moving-iron cartridges (Grado cartridges), but it will not handle low-output moving coil cartridges (although it may have enough gain for high-output moving coils).

If you don't mind an unsolicited suggestion, it is probably past time for an upgrade from the 2270. While the 2270 was a very good receiver in the early days of solid state electronics, it is by now very dated. Since you are getting a new turntable, and therefore are presumably interested in having a high-resolution audio system, your next step in upgrading your system should be your receiver. Fortunately, there are some good receivers and some excellent integrated amps (if you can live without the tuner) available today. Look through the Audiogon archives for suggestions about receivers and integrated amps.