Don't forget, those old 78's (including some early 33's) don't use the standard RIAA equalization curve which is what your current phono stage has. The curves varied by record label (Decca, RCA, etc).
there aren't many phono stages that handle EQing across the years. Those that are out there are pretty darned pricey. The two that come to mind are Graham Slee Jazz Club and the KAB unit.
I own the Slee. I'ts a wonderful sounding unit. In the end what I ended up doing was setting up a dedicated 78 system. I use a Stromberg Carlson AR-425 amp (PP 6L6) that has an integrated phono stage (variable eq'ing), a Dual 1229 with a Shure V-15 and 78 stylus and an Altec Iconic speaker (the 624).
It's loads of fun to listen to. I still drag home 78's that I find in junk shops and flea markets. I've limited myself to mainly jazz and blues from the big named artists (anymore).
When it comes to your question of new cart or retip, go new and cheap. Reemeber, these are 78's. Granted, I can get some decent fidelity from a select few of my 78's but the vast majority of them have been worn out by the old steel needles used way back when. Honest to goodness, cheap is good in this case. I'd even consider a crappy Shure M-91 (or 92, whatever the number) and the 78 stylus. You could get into that for about $125 (or so) bucks.
On the other hand, if you are interested in picking up a dedicated system, just so happens I know of one you could get one pretty resonable (I need more room, not more stuff)
Drop me a PM