i have been upgrading non stop, but keep in mind you cant just upgrade your sub stage, learn more and more about your front stage too.
as i have progressed through audio, i have come to realize they my front stage is the most important thing to me as of now. i spent the most time on it, put the best work into it, and it showed in the end.
but as far as my subs go, i always want bigger and better with a ton more power, and i have been doing that, im running a single 18 right now off a 3000d, but i wanna make the switch to a single 15 off more power.
youll get there eventually, just start saving your money now, because as soon as it hits you, youll wish you had more money.