Will having the subwoofer a good 25-30 feet away from the central hub effect anything because of the wire length? I am going to have to cut the existing wire and make it longer with speaker wire. It's a HTIB subwoofer, and it's not very powerful. My living room is big and the bass doesn't carry well so I want to put the sub right by where we sit.

Longer wire.............. none.
If it's an 'rca' cable, you don't have to cut it. You can couple two cables together. Most 'HT' subs have 'rca' cables.
Link to coupler........
http://www.radioshack.com/product/index.jsp?productId=2427997&cp=2032058.2032231.2032280&pg=2&searchSort=TRUE&retainProdsInSession=1&y=9&s=A-StorePrice-RSK&x=16&parentPage=family

I don't think you'll notice any difference whatsoever going to a 25' cable. When you get into really long runs you may, but 25' isn't bad. Also, if you do get couplers I wouldn't necessarily get the cheapest they have. I know most places don't exactly have huge selections, but I've had humming/interference issues with the cheapies before.

As long as the cable is 75ohm and is shielded to prevent RF/EMI then you are ok.

Longer wire.............. none.
If it's an 'rca' cable, you don't have to cut it. You can couple two cables together. Most 'HT' subs have 'rca' cables.
Link to coupler........
http://www.radioshack.com/product/index.jsp?productId=2427997&cp=2032058.2032231.2032280&pg=2&searchSort=TRUE&retainProdsInSession=1&y=9&s=A-StorePrice-RSK&x=16&parentPage=family

The sub runs on your run of the mill black/red speaker wire.

That's unusual................. :rolleyes:
Then you have to 'splice' both wires together, or buy adapters that can be used with the bare wires. There are some 'bananna jack' adapters that you can use, if you wish.