Are you seeing image problems with your Hellios? Fuzzy corners, too much coma, chromatic aberration ...? If not, then there is no need to replace the lens.

If you see optical problems with your present lens then the Takumar would be a very good lens to replace it with. The Takumar will work just as well on a Praktica as it will on a Spotmatic. Unless you are having problems with the Nova body there is no reason to replace it - your pictures will be no better.

Spotmatics are beginning to really show their age so budget for the cost of a strip-down and relube - $100 and up - if you are going to buy one.

As to snob appeal - a Praktica has more cachet these days than a run-of-the-mill Pentax.