I've considered a larger achro for the same purposes that you suggest. I didn't do it in the end but I had done enough research to decide I would want something slower than f/5. The Bresser scope mentioned above is around f/6, while Explore Scientific do achros at f/6.5.
You can get the HiOptic 127mm f/6.5 for $720:
http://www.telescopes-astronomy.com....-refractor.htm