I have a Leica R 50mm Summicron converted to fit an A mount and also am going to pick up a 90mm 2.8 that gets awful good reviews. The 90mm has been called optically perfect. It is very easy to convert just swap the mount and remove the aperture lever thingy. You can get adapters on Ebay all day for almost nothing.
If you watch listing on Ebay or Craigslist sooner or later someone will put up an older Leica R mount lens at a bargain price. This is an easy way to get great glass on a smaller budget.

Summicron 50mm by Cosmonaut's, on Flickr