After ruining my 305 by jumping back into the water after Eagleman (a little woozy at that point) - I found what I think is a pretty good deal on a new 310 with HRM. Ebikestop.com has them for 329 no tax. There is also a Garmin 50 dollar rebate on form on their website...it made a great father's day gift - from me to me!
Did you try Pacers - they give club discount on Garmin.
I bought a Nike Sportband at Pacers at Christmas time - loved the low tech side of it - however, first sweaty day this spring it shorted out. I bought it back to Pacers and they gave me full store credit. I upgraded to the Garmin then. Great customer service and they have an in store guy that will help this tech challenged gal set it up. Great customer service is worth an extra $50 and support a local club retailer. Think about it.
Concur - I buy all my shoes and other stuff there...they have a military discount as well!