Congrats, Lord Davon. I'm glad you got the most out of your blu instead of returning it.
By the way, as far as the RMA thing goes, I don't know how it works with an entire kit, but I don't see why it would take much longer. Anyway, when I returned my pack and batteries(two separate occasions), it only took exactly one week from the day I took them to the post office til the day they arrived in my mailbox.
I'd say if you already have 510 cartos, get the 510. Also, I don't know of ANY kit you can get for just 25 bucks for any model e-cig. And sine parts are compatible with your blu, if need be, you can swap out parts. But keep in mind, I know nothing about KR-anything. All I've used are the blu, the 510, and "firelight," which if I remember correctly is a 403. It wasn't much better, if at all, than the blu. Unless someone here has used 510s and KRs that can offer a reason why the KR is better, I say get a 510 unless you want to go right to an ego or some other bigass thing. That's all your choice. Whatever you do, good luck and happy vaping.