Should i solder wires to Sub or no?

Don't turn the heat up too much and keep the soldering iron on it long enough to get a good solder joint, but no longer. The heat can easily damage coils if you leave it on too long. I soldered to my subs too because the crimp connectors kept coming off even when I used pliers to make the connection even tighter. Speakers need to start using full sized tabs if they don't want to use binding posts, damnit.

Hey, there's an idea, solder on some binding posts.

I personally like to be able to quick-disconnect speakers from the wiring.  So it's F-disconnects for me every time I hook up a speaker.  It's important to use the right size, and sometimes you have to buy 2 or 3 sizes to have the proper disconnect on hand.  Matched up properly, the female disconnect and the spade will fit tightly, with a click when the locking tab on the female engages the notch on the spade terminal.  Sometimes just a slight squeeze with needlenose pliers is all it takes to make the connection snug.

The disconnect may be soldered (and crimped) to the wire, if desired.  Mostly, a good crimp with a crimping tool is all that is needed, though.

http://www.partsexpress.com/webpage.cfm?webpage_id=3&SO=2&&DID=7&CAtid=41&ObjectGroup_ID=400

Make sure the solder joints are not cold. They should be shiny, not dull.