^^^This. Either get more T1's if you want more, or get a different type of woofer. Are they in a prefab box? If so, building a properly designed box for those will usually yield more output, without paying for more woofers.
Yeah I combined subs once, thinking that it'd be okay cause they were about the same power. Not only is it a bad idea, but it's nerve-wracking to think that something may go wrong.