Is the $1,000 budget the total budget, or just for the subs with more money to spend elsewhere?
What is the rest of the system? So far it sounds like you need probably to get a new amp, and box too. Curious if you have the rest of the electrical ready to handle it.
Just read that most recent post again. Honestly you could spend $1,000 on a new alternator, battery, wiring, and other things (like distribution blocks, fuse/breakers), and get to $1,000 before you ever even start spending money on amps or speakers.
Do you have an idea of how far you want to go with your system? How much total/how much more do you plan on spending on it?