From lehmann blk cube to Nova Phonomena with...?

Some folks do make upgrades that are questionable, or even go backwards. But the Nova Phenomena is a lot better.

I've had both of those cartridges my self. Moving up to the 20 will be a big improvement by itself. As far as the phono preamp upgrade goes, I would go a different route.

Its less money, but I would get a DV P-75 phono pre instead. Needless to say, its a good match for your new cart.. Use the money you saved and buy a Rega power supply/speed stabilizer. That should make a much bigger difference in SQ.

@ Zd542: thank you for the advice, I was thinking myself to get the P75 (due to the ideal match with the cart, as you said), the problem is the cost of the same too high in my country.
BTW, I already own the external power supply for the P5 but I was thinking to get also the Groovetracer subplatter (and the others upgrade).

If you already have the power supply, I say just get the best phono preamp you can afford. It will make the biggest difference.