Another means to weld is friction welding with filament attached to a dremel, or a simple 3D printing pen.
Ultimakers are great machines, if you are going to start with low budget I recommend the Ultimaker Original. You can modify it for dual extrusion.
The Ultimaker 2 borders on a professional level printer so if you have the budget that is wonderful.
Otherwise the Cel Robox is a good printer at $1k, with dual heads, enclosed volume and more reliable than Flashforge, though I agree, I would also choose the Flashforge over the Ultimaker 2. If you print a lot with ABS I do recommend installing a ventilation system and using it in a room where you don't reside.