So I went to install a rear strut bar I bought off of ebay... And it looks like to install it I would have to cut up the trim panel around the strut tower. Is this normal for rear strut tower bars?

 

Yes.
You must either take out the rear panels, or trim a hole for the strut bar to pass through

 

lol, yeah dude

 

if its one of those cheapy *** bars...I wouldn't bother cutting up a perfectly good panel. Those cheap bars flex like there is no tomorrow. Save up and get some good suspension if you want to feel a noticeable change in the way the car handles. or at least buy a quality bar

 

Ditto. Those eBay ones are utterly useless. It's classic ignorant bling lol

 

Thats true but the cheap braces can be made more ridgid if you have a welder. You can weld up the pivot points of the bar (tack weld it while installed).
but yeah some nice springs and shocks will do a lot more than this bar but thats not your question.