RGA8 came with pickups that take AA batteries, they sound like, well, the worst thing i ever heard. Made an Axe II sound bad. LOL
808x's will be a super easy install. Drop in replacement with little-to-no soldering. I haven't played them personally, but I've owned the 808s and they weren't too bad, especially if you 18v mod them. I currently have a D Activator 8 and PAF 8 in my RGA8, and they've been a huge hassle getting wired in from scratch, so I'm thinking about doing a fresh start with some 808x's. I like what I've heard of them and people seem to really dig them. Kinda between actives and passives.
That being said, the DA8 and PAF8 sound awesome. My favourite 8 string pickups I've tried so far. If you're comfortable with wiring a guitar totally from scratch, or have a tech you can take it to, they sound killer.
808s aren't amazing, but definitely aren't bad. If you can get a set cheap and don't mind their 6 string stuff, it's definitely worth considering.
Blackouts were too hot for me, but not too bad. More organic than the 808s, but really hot and felt kinda bassy.
I had a Bare Knuckle Ceramic Warpig 8 and it was really neutral and good sounding. I've liked all of the BKP stuff I've heard, but I liked the DA8 more than the C-Pig, so unless you're in the UK, or can get them really cheap, or really want them, I'd go DiMarzio.
TL;DR: 808X, probably, IMHO