Your prints come out really good for a $150 printer. This is my last one that I designed in sketchup for one of the STEM classes I teach.
If only the Roman's had 3D printers... It is 77 pieces that are designed to snap together. Ran out of green in the middle of the print and had to switch to yellow. But it was designed to show the students that if you can imagine it, and know how to design... you can make it and it will work.
Have you tried any post processing? For PLA and ABS an acetone vapor bath will increase the strength of the prints pretty significantly. Muriatic acid vapor bath will do the same for nylon filaments.
As for printing metal, I just use shapeways3D.com. Their microject printers have a resolution of like 0.0001 mm so there are no visible layers and the prints are very strong and have dissolvable support structures which leave no marks on the print. The metal prints can get pricey, but for a prototype they are worth it.