Evan,
If $ 2k is your budget and CE-1000 is all you have (for now) to power new subs, I would suggest you take an alternate route. With $ 2k you can purchase (as an example) 2 Yorkville Elite LS800P's. They are self-powered 1500 watt single 18" with a street price at about $ 1k each. They are excellent self-powered subs but do weigh about 145 pounds each if that is of any consideraton for you.
If that's pressing your budget too close, or if the LS800P is too big for your liking, consider the Elite LS700P. It's a self-powered 700 watt dual 10" with a street price of around $ 750. So two of these put you well within your budget. They also weigh 95 pounds or so (50 pounds less than the LS800P) but of course don't have quite the same output as the LS800P (about 3 db less) but still very capable little subs. I believe either one would be an excellent match for the 3-way Mackie 1530's.
You mentioned getting "real" mains someday and I am not sure what you had in mind there. But if you have something specific in mind as "real" mains for the future (i.e. EAW, McCauley, Turbos, Yorkville TX?) it would be wise to take the sub purchase into consideration now. These subs are a good match for your Mackie's but wouldn't be your first choice for a larger touring system.
ScottH