Rega P9 - need help selecting the perfect cart.

I will soon be in the market for a new cart for a Rega P9. I'm currently using the Exact but would like to try something else.
Seeing as cartidges are a little hard to audition, I'd like to hear from anyone with a P9, and try to put together a short list of carts maximum price $1500. I'd really appreciate it if anyone could answer some of the following questions.

1. What cart are you using? What are it's strengths and weakness. (In your system - I know it might be different in mine)

2. If it's an MC - what loading sounds the best? (I currently have an EAR 834P. loading for MC is 510 ohms - I'm considering replacing the phono stage with something more flexible, unless I find a cart that likes either the 510 Kohms for MM or 510 ohms for MC)

3. Are you using any spacers - shims to raise the tonearm? if so how many, and how did you figure out how many you needed? (measurements or trial and error)

4. What is the required tracking force? (I do not want to have to get a different counterweight, so I don't think I want anything that tracks over 2g) I could be wrong on this, but I'm just thinking I don't want to go right to the limit and have the counterweight right at the end of the tonearm.

5. I cannot find effective mass of the RB 1000 tonearm. Does anyone know what it is, so I can figure out compliance, or should pretty well any cart be compliant with this arm? Are there any carts that I should avoid with regards to compliance issues.

Thanks to all who took the time to read all that. I'm kind of new at this cartridge setup business, so if I am way off track (no pun intended) on anything, please let me know.

I have a dynavector XX-2 on my P9/RB1000.
I think I have 2mm spacers under the arm, but they could be 4mm. Dynavector is a great match with Rega.
Do you have any ideas about the kind of sound direction you want to go in? Is there anything you don't like about the exact?
Piedpiper: Resolution and neutrality are important. Dynamics and Detail are important - but not to the point of being scary or anyalytical.

I listen to all types of music so I want something that will give me natural sounding vocals and acoustic music, as well as hold together for orchestral works. I want to be able to separate the instruments, and pick up on subtle changes in mood.

Good imaging and stability are very important (no strolling violinists), as is accurate tonal quality (no tricks or special effects). Anything that hints of brightness is out. If the cart has anything to do with it, I like when the music spreads out and fills the room.

The Exact I'm using had about 10 hours of glory during the break in period, but then it (or something) went sour, and now I get something different everytime I use it and it's usually not pleasant.

I'm losing my patience with it so I want to start thinking about something else. Sorry about the goofy terminology, but I don't speak audiophile very well. :(
I use a Benz Reference Silver on my P-9. But my set up is a bit different. To save money, I had my modded rB300 arm from my old P-3 mounted onto my new P-9. Cardas clips, cardas wiring, cardas female rca "box" added to back of table, using Benz PP-1 phono unit, Cardas golden cross interconnects. Works well for me. No spacers that I'm aware of. I think tracking force set somewhere between 1.75 and 2 g. Had my dealer, Savant Audio, set everything up.
I have heard that Dynavector Cart's. sound good with the Rega tables. I would buy the best you can get for the P-9.