Upgrade suggestions

If your preamp is the Ayre K1, it probably has a phono preamp in it...line 2, but maybe not indicated. If it doesn't, you can get Ayre to put one in...I don't know the cost, but it is a fabulous phono stage.

One of the challenges when asking for advice on Audiogon is that you often get way more good advice than you can practically (or financially) act on. ;)

There are a couple themes that run through the suggestions that have been made here I'd highlight to you -- first, your turntable and arm are fine -- don't bother replacing them. Second, an important part of upgrading your sound is getting a couple essential accessories -- a good alignment protractor (as Macdadtexas suggests) and (I would still argue) a good record cleaning machine. To which I would add, on reflection, an Onzow Zerodust to clean the stylus on your cartridge.

There seems to be a consensus that your GCPH phono preamp is a good fit for the rest of your system (I had suggested a phono preamp upgrade, but bow to the collective wisdom of the other respondents).

Then, look for a good cartridge upgrade oppotrunity. I agree with those who suggest a used cartridge from Audiogon is a definite option, but second Coltrane1's word of caution -- purchase only from a seller with pretty hefty positive feedback -- a lot of used cartridges have been abused. The biggest challenge you face is that phono cartridges, like speakers, have real personalities and make performance/price trade-offs. So you may want to set your purchase price range to allow you to pick two or three, and purchase them one at a time, as Coltrane1 and Lak suggest.

Hope you have fun with your upgrading.

Rdavwhitaker,
I agree with all of the feedback you have received.I've owned many Rega tables (& still use Rega tonearms).I always found the Rega cartridge to be the weak link in an all Rega turntable set-up).I found The well reviewed and very affordable Ortofon OM-30 Super to be a significant improvement over the top-of-the -line Rega Exact.Other cartridges that have worked well for me with stock and modified RB-250 & 300 arms are the Dynavector 20x,Clearaudio Virtuoso Wood,and Ortofon 2M Blue & Bronze.All of these cartridges cost under $1000 (The Blue and Bronze are less than $500).

On the other hand,a new table can be fun.The Marantz TT-15S1 comes with an $800 Clearaudio cartridge and retails for less than $1500.I've seen them used for as low as $750.I got a great deal on a new Acoustic Signature Manfred with an RB-250 arm.
Vintage tables can be fun as well.I've been collecting Dual CS 5000 tables(I have 4)and just acquired a Thorens TD 125.The 125 fitted with a Rega or other fine arm is supposed to be a World Class Table!

Sorry about the rambling.

Thank you all for your responses. I think that I will try another cartridge.
It is nice to see the Rega P5 so well regarded. One of my issues was speed stability, particularly at the end of a side of an lp. I bought their outboard power supply which was supposed to be an upgrade in speed regulation, and I detect no audible difference. I was wondering if another manufacturer was better in this department, such as VPI.
The reason that I don't listen to more vinyl is the "software" issue. Nothing is more satisfying than a pristine lp, but I'm tired of buying at stores, ebay, etc and getting the usual 40 year old warped discs. I have cleaning fluids, brushes, etc, and the Rega record clamp, but I still find those issues limiting.