catridge match with Morch DP-6

The DP-6 is much better than the DP-4, I'm told. I'm afraid I don't know how it would stack up against your Rega, but it is probably somewhat better. Is it better enough to justify the cost? Of course, that depends on how much you pay for a DP-6. BTW, I am told a very good upgrade from a rewired RB300 would be the Clearaudio Unifi, which retails quite reasonably. The Unifi is said to be a pain to set up, though.

You don't mention what cartridge you have now. Since the Rega can take a very good one, any of the cartridges you mention would probably work fine in the Morch. Again, though, are you aiming at enough of an upgrade? Small upgrades can work out very dear. You might consider going for a very good cartridge indeed--your proverbial "last cartridge", perhaps--and putting off the arm upgrade.

That's what I did. I swapped my Glider 2 HO for a Cardas Heart. It sounds wonderful in my rewired RB300, and it will sound even better in my next arm.

Hi, when I was buying my VPI turntable at my dealer in Seattle, I had a chance to compare the Rega, Morch and VPI tone arms using a Glider2. The Morch sounded much better than the Rega. So I bought the VPI with the Morch and Glider combo. Sonically I was very happy, BUT I couldn't live with the Morch, due to the construction, It's called the worlds lightest tone arm for a reason, each time I used it, I thought it would fall apart, it just felt flimsy with all the weight strings. I sold the Morch and bought the VPI, much happier. The gentleman who bought the Morch also kept if for only a short time, he had the same complaint, flimsy and the weights were hard to keep in constant balance.

I have a Morch DP-6 with a ZYX R-100 mounted on a Oracle Delphi Mk 5. The combination is very nice (slightly on the warm side, good detail and a very silent background) after a lot of tuning.
Improvements I have made included a 2" thick granite base, detailed tuning with proper measurement and setup tools done by a friend, and experimenting with the loading on the phono preamp. I use the standard Morch phono cable but someone suggested that it could be greatly improved upon, which I am in the process of doing.
I have even been in contact with Hans Morch himself and he uses a Ortofon MC 3000 with the DP-6 on a Morch turntable, which is not being produced anymore.

I would go with the Kontrapunkt B or the new entry level Allearts.

The Morch DP-6 is Dual bearing tonearm is way better than the Rega 300B. All the cartridges you mention should work fine with it provided you match the proper Morch arm tube to their weight. There are 4 arm tubes to choose from Light 3.8g, Medium 5.7g, Heavy 7.4g Extra Heavy 13.1g.
As far as the counter weights going out of adjustment they are held by orings which must of been worn out on the Morch arm mentioned. I have had mine for 7 years on a Sota Sapphire with no such problem. I am using a low output Benz Scheu catridge.