Cartridge reccomdations?

Masterplan, I suspect that you would get far more bang for the buck by improving record cleaning first. Going from VPI 16.5 record cleaning to ultrasound was a bigger difference, for me, than going from high end MM to higher end Koetsu.

The added advantage of record cleaning is that you are likely to increase stylus life, because the grunge in the record groove tends to contain diamond dust. Or so I have read. YMMV

Hi,
You can't go wrong with a Lyra cartridge.  I have owned a Delos for several years and really enjoy its performance.  The diamond/cantilever assembly is manufactured by a company in Japan that makes scanning electron microscope tungsten tips so they know how to work in the micro world.  The Delos replaced a Benz Glider.  Both have a Boron cantilever, but different diamond stylus.  The Delos being a line contact, meaning the tip rides in the record groove at one small specific point.  The only hic up is 'fuzzing' of the paper belly cover.  Not a big deal.  
What type of phone stage do you have and can you select various gain/loading points?  What type of arm do you use?  Loading and Gain and arm mass are very important when selecting high end MC cartridges.   Give the people a call at 'the needle doctor', they can help you out. 

op

u need to provide a lot more info to get helpful responses

system? in particular phono front end and amplification

budget?

Thanks for all the great responses! My system consists of a brand new VPI Scout II with the JMW 10 with anti skate and VTA, the aforementioned Shelter 501 III, VPI SDS, Simaudio Moon LP 5.3 phono stage, McIntosh MA6500 amp (I used to run a BAT vk30 to Cary CAD40m's and like this much more for my musical taste), and Mark & Daniel Apollo II speakers. Everything is powered through the PS Audio Power Plant 3 via Audioquest NRG-2's, 72v (upgraded) Audioquest Columbia RCAs and Audioquest Gibraltar Speaker cables. Everything is well-isolated on spiked custom made 3" hard maple butcher blocks...and I do have a VPI record cleaner which I use religiously. I love the way it all sounds now but, as it goes with our kind, I'm always looking for a little more.  Thanks again for the great input!

Upgrade to the 901.