Yeah, Express really doesn't cut it as anything more than a musical notepad.
I own a legitimate copy of FL8 XXL, and of you got the money it's definetely the way to go. The plugins it comes with are easily worth the price on their own, especially Sytrus once you get past how complicated it is.
If you use mostly free VST's however, the producer edition should be just fine, anything lower and you're losing vital features if you plan on using FL a your main DAW.
If you just want to use FL inside another host, however, you might be fine with the Fruity edition.