the first thing you need to know is a dealer is not going to give you what your car is worth,2nd the 05 honda is going to be priced way more than it is worth.i would say if you trade you will be looking to finance at least $10,000 more or less.
Yes, that sounds about right. Check Edmunds.com or www.kbb.com for the approximate dealer value of the '05 you are considering and use that data in your negotiations with the dealer.