I'm guessing some things....
1) your place is carpeted right? Even so..... go get a carpet sample (2x2 piece or so) and place it under your sub.....
2) the sub you're looking at is faster, and more accurate than your current one, so I don't think it'll affect the neighbors anymore than your current one does.... I'm assuming you don't keep your current sub turned all the way up, so you'll be listening to the new sub at the same levels, it'll just sound better
I'd get it.... Good sound doesn't have to be loud..... The low frequency stuff will travel through walls though, so make sure you grab an extra piece of carpet, and keep the sub further away from walls etc.... (get some bass traps too)