There's a question that needs a question. Define practical? How and where do you ride? 2 up or just yourself? Touring, commuting? Need performance or comfort? Do it yourself maintenance or done by the shop?
You can find nice examples of both the ST2 and the ST4 in that price range. You'll just have to ask yourself if you want the better suspension and more power of the ST4 or the cheaper maintenance and lower inital cost of the ST2.
Edit - I have no idea where you are located, but a quick search on eBay had this interesting example show up....
Terry spelled it out pretty well. The ST2 can be had really cheap, they make nice power down low but get flat before you run out of tach- the ST4 is gonna be a few bucks more but makes more up top. Either one is a great bike. The ST4s may be a bit out of your range but offers good power down low and really comes to life when the ST2 dies away. Post you location, maybe someone here knows someone who knows someone that has something for sale.