Google for a decent phono stage. Failing that, I use a hi-fi amp for my general listening in the sitting room that has a phono stage built in. I also have all my other media stuff in the room connected up to the amp, so it's the central hub of my set-up. If you have a lot of media stuff in one room, bluray player, laptop, turntable, some form of cd player, dvd player, then it's definitely worth buying a dedicated amp for everything to go through.
Otherwise, get a phono stage.
Your BX5A's will sound excellent with vinyl. I use my KRK RP5 G2's with a set of 8" hi-fi speakers. The RP5's provide the detail, the 8" speakers provide low end and a smoother sound to balance out the KRK's slight sterility. But before I acquired the extra speakers, my KRK's on their own sounded great. So no worries there.
And I have a lot of stuff on vinyl that was recorded digitally and for the most case, there's a slight improvement, bit more detail in the transients, a little bit more open, but I've also got digitally recorded stuff that sounds worse on vinyl. It varies.
All of the stuff I know was recorded analogue generally sounds fucking monumental. The thickness of the record also comes into it. All my stuff by Sunn is 180gram vinyl and it feels sturdy as fuck.
It also varies between label to label. Most of my Relapse stuff is pretty... Well it's okay but could be better?
All of my Southern Lord stuff sounds fucking incredible.
You get vibes from certain bands or labels or musicians where you know they're passionate about vinyl, just a gut feeling, and those bands you can generally be sure the vinyl will sound incredible, but otherwise there's generally an improvement. Most of my record collection is made up of more obscure stuff generally because the vinyl's better quality and limited edition and worth owning. Some people buy just EVERYTHING and ANYTHING on vinyl. What you buy and don't is your choice
Hope that helps somewhat dude.
Also look into an eliptical stylus for the best quality playback. Hit me up on msn if you want any more advice.