Hi mate, I was looking into this myself a little bit, and I know someone on here did do this and ran it for a while with positive comments.
I have removed mine but only worth my gtr backbox, not the standard box, but I can say it did make a big difference (in a good way. Really opened up the backbox, and only added minimal drone if any.)
From what Iv seen, from videos like the ones youv posted, I think it makes it a bit louder, add some rasp (some say it's good, some disagree) and as a con, mayybe add a little bit of drone. But I like it!
For the cost of the mod (£10 tops for tube, hours labour max at a garage?) I say give it a go, although I'm sure many will say just get a proper system. But you Havnt much to lose by giving it a go.