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.
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.