I don't know what your definition of "budget" is. It might be helpful if you post a price range.

If you were able to afford the latest version of a 50 Summicron, you can afford the Zeiss ZM 35/2 Biogon. I bought one used for the same price I paid for my 50 Summicron (latest version) on eBay - or about half what you'd pasy for a used 35 Summicron, 4th version, or 1/3 the price of a used 35 ASPH. The grey market price of the Biogon is about the same as what a used 50 Summicron (latest version) costs from a dealer.

Good luck,
Bill