A HK 310 would be pretty outdated. You may want to go directly to Harman Kardon's ebay site and purchase a newer model that ends in 25, 30, or 35. Here's a link
to that store. When you buy from them you get a full warranty. They don't have anything for you right now but the site updates every couple of days.
As for speakers Buckeye will suggest
BIC America DV-62SI unless I am greatly mistaken
. They are right there in your budget and are supposed to be some nice over-achieving speakers.