Tony, one basic question for you: why not just keep GMail Notifier running? On my system it's only tying up 8.5MB of memory, and I can always be notified of new mail.

I think we should really keep this as straightforward as possible. Just install GMail Notifier, and follow Bitt's instructions for adding your other email account to GMail. I have two accounts set up this way myself, in addition to about eight forwarded addresses. GMail is an amazing email aggregator, and as an added benefit, your other email addresses get the advantage of Google's spam filters and search features.