How old, Tom? If it is 2003-2005, anything under $3500 would be reasonable. If it were mid to late 90's, it might be more like $2500. I would expect a price around $6K for a brand new stock Europa these days, so nearly new and near mint might even be a little higher. I must say that I haven't been paying as close attention to actual sale prices these days, so I could be off here.
Ash would be a non-standard body wood, though probably not an up-charge. Walnut over ash probably provides a nice middy growl with a little crispness on top. Since you've played it, you already have a good feel for the tonal capacity of the instrument.
What it always comes down to on price, though, is the mutual comfort level of both parties. A Europa six would be pretty rare on the used market to begin with. With the replacement cost around $6K, I wouldn't feel bad about paying even $4K for a prime used model that has all the features I wanted. If I keep it to play, it's worth paying a few hundred over street value if that's what it takes to put it in my hands.
