There are a number of good accounting packages for small businesses. QuickBooks, of course, is the most dominant. In addition to being an easy to use general accounting package, Intuit is coming out with new vertical versions (retail, manufacturing, professional services to name a few).
http://www.smallbusinesscomputing.co...php/3291551%20
PeachTree also make several versions that are good for small businesses of varying sizes starting from 1 or 2 person shops.
http://www.smallbusinesscomputing.co...php/3071271%20
Intact, NetSuite, ACCPAC are other names worth researching.
Also, if you are a member of any trade association, you should ask them what they recommend. There may be vertical accounting applications built for your type of investment firm. Or there may be resellers who customize one of the above packages for your industry.
Just a few thoughts. I'm curious to hear what others have to say.
--Dan