Soluble support material is something that industrial machines like the Stratasys Dimension have offered for some time now, but that the cheaper "pro-sumer" machines are still struggling with. One can support overhangs with the same material that's being printed, but this leaves a surface that needs to be cleaned up afterwards by hand, using tools like clippers and grinders. There are also various combinations of materials such as PVA and PLA or ABS and HIPS where the supports are supposed to dissolve, but these often have problems with adhesion, registration or waste disposal, as well as some of the headaches due to improperly implemented dual heads noted in your post. Some manufacturers claim to have solved these problems, but you'd be well-advised to require some proof of this before purchasing. Unfortunately, your stated budget is not enough to get you an industrial printer; the annual maintenance cost and supplies for one of those Dimensions would come pretty close to consuming the whole amount you've allotted.

Andrew Werby
www.computersculpture.com