The existing cable should be fine.

I don't have any good advice as far as coming up with a story to tell the wife. I would be tempted to tell her that the sub and speakers came as a "package". This may not fly.
For me being honest works good most of the time.


M80's VP150 QS8's Earthquake SuperNova MKV-15
Integra DTR-7.4 Outlaw 755 Outlaw M200's Outlaw ICBM