A nice thing about Soft Synths is that there are many free and inexpensive ones available. Brainspawn's Forte Solo is a good free host for testing VSTi's, although you will want to migrate to a non-free multi-timbral Forte eventually. ComputerMusic magazine, FutureMusic magazine, and MusicTech, have all provide soft synths as part of the purchase price of some or all issues of those magazines. Some top softsynth companies like Native Instruments and Virsyn and SampleTank have made free synths available (I guess to attract interest in their commercial products). There is even the Free Synthedit that allows you to design your own softsynths.
Also, there is another plug-in format called Buzz with a free host and many free plug-ins. The Buzz host also hosts VSTi's. So, you can waste a lot of time with very little money.
[This message has been edited by Clif Anderson (edited 01-10-2004).]