I wouldn't get an 8" f4 for visual specially as you already have a 10". What about a 100 ed refractor like this
http://www.astronomyalive.com.au/ref...telescope.html or for $400 less an 80mm ed and get a pre loved eq5 mount. My 100ed gives very similar views to my 8" f5 Newt, but much easier to get carry around. Depends on what you want to do with the f4 photo or visual? I don't have but have heard the 102mm f9.8 achro refractor is a great scope and still in your budget, check out Skywatcher refractors at
http://www.andrewscom.com.au/site-section-10.htm.