Itching pretty bad for a supersport...

I've been riding a year now on my 2007 GS500F, after taking the MSF BC. My bike has served me well and it has been a great bike to learn on! I commute on it between school and occasionally like to meander around back roads, or take short trips. My little GS has been bulletproof and very forgiving. If I hadn't started on such a forgiving bike I know that my lowside when I first started riding would have been much worse... I've learned how to do all the basic maintenance on it myself (with my awesome girlfriend's help, as she's been getting into bikes lately too!) and I have become very comfortable with the bike overall. But I do a fair amount of highway riding and the GS just doesn't cope as well at those speeds. The acceleration has also started to feel slow and kind of dull. My truck gets up to speed faster :/

Bottom line is I've been really wanting a supersport lately. Bad. What should I expect going to an i4? What are some good, inexpensive options to look at considering I would sell mine? What do I need to be careful of? And how can I try out different bikes before I buy one?

TL;dr: wanting a supersport after rising a GS500F for a year. Help please!