Ditto here. The sub is a really nice thing to have, but not essential right away and can certainly be added later. If you dilute your start-up system to divert $$ for a sub, at SOME point, you'll be unhappy with the compromise made by saving initial $$ on the other speakers. That will eventually become an expensive itch to scratch.
If you opt for the M80s (BTW, the M60s should be well beyond adequate for you), there may be an increase in the amount you must spend for a receiver since you will need to assure that it can drive 4 ohm speakers.
