I have a GSO 8" f6 dobsonian, as well as a GSO 8" f4 imaging newtonian that I use with a NEQ6. To be honest im not sure i'd really call the 8" f4 significantly more portable than the f6. The f4 has a larger secondary mirror (70mm vs 50mm) which reduces contrast slightly when used visually. The dob also comes with eyepieces, whereas the imaging scopes do not (and as other have said, the 'imaging' scopes require extension tubes to bring eyepieces into focus).
If you wanted a newtonian alternative to the 8" f6 dob for visual, you could consider the GSO 150mm f5 "imaging" newtonian, perhaps in conjunction with an EQ3 or maybe one of the GSO Alt-Az mounts (if these are appropriate for the weight of the newtonian). This combo would set you back about $600-650ish (see
http://www.andrewscom.com.au/site-section-10.htm) + any eyepieces/extension tubes you needed.
Alternatively instead of the newtonian you could go with a refractor (I also have the Long Perng 80mm f6 achromat which is a fine scope, especially for the price, but does not include eyepieces or a finderscope), or maybe a 127mm Skywatcher Mak-Cas on an EQ3, although both of these options would be slightly more expensive.