I'd like to follow this conversation for the same reason, too. I'd posted a week or so ago in the refurbished thread asking for suggestions. I got my friend an SD3-12 last year with the SA cone/spider upgrade and am giving it 600W RMS. She likes it but wants more low end and wants more power in the future. So my original question was do I upgrade her to the SA or jump to the U. But now seeing the comments here, I'm wondering if I should spend the $50 more for the X v2 refurb instead. It honestly seems like the better deal. They both handle the same power and even though for the present time my friend would be still powering it with the 600W RMS, when I went to upgrade her we could get it the power it needed. So if that's the case, for just a little more, it looks like the X v2 is the better deal and sub to go with based on the comments of it being more musical and low than the U series. I'd build a new box for whichever sub she goes with so it's not an issue of a drop-in replacement. Just which is the best one for the money to go with in the long run. So 1.) would either the U or the X v2 sound ok on 600W until we got her a more powerful amp? 2.) for the money, is the X v2 refurb the better deal in the long run?