which cartridge to buy? so many...

The Shure V15VxMR -- the "Rodney Dangerfield" of high-end phono cartridges -- is an excellent cartridge and can be purchased new for about $275 from Garage-a-Records and Jerry Raskin's Needle Doctor. I have owned many cartridges, and the V15VxMR holds it own against many more expensive models.

An Audio Note IQ-2 is a OEM version of the Goldring 1042, and can usually be found for less than the Goldring. If you could find a inexpensive step-up transformer for around $100 or less, you could get a Denon DL103R low-output MC cartridge, and really get cookin'!
Another possibility is the Audio Technica OC-9, if you could find it sufficiently discounted, or the Ortofon X5-MC.
And don't forget the Denon DL-160 as a possibility. It is high output.

For the money, the Ortofon X5 is really hard to beat ($115 from Hong Kong). For rock music you might want to try a Stanton, too.

Be sure to use a cartridge compatacble with the Rega. Dynavector is one of several that works well with the rega. Many people say that Grado has hum issues with Rega. You might also want to stay with a MM cartridge with the Rega 2.

Dynavector 10x4, no question.