You can always use a colour correction filter for better blacks and more contrast (with recalibration to D65), or a simple ND filter (no recal needed if you're happy with the image) to improve blacks and reduce the image brightness to something more cinematic if that's important to you. Adding a filter to reduce the image brightness may also have the side effect of reducing the rainbow effect.
I can certainly vouch for Gary's suggestion of an ND filter - I use an ND2 on my W1070 and black levels improve, the whole image takes on a more cinematic feel and the shadow detail is enhanced. (other than that I use Smart Eco and just a quick set up with THX optimiser)
The main thing budget projectors lack is better control of their brightness, if it had an iris control, it would be brilliant, but it would also no longer be "Budget"
I'd say the W1070 (basically the same, with a different lens) is on a par with my old Barco GB808S CRT projector.
That's interesting, about the rainbow effect! I don't see it, so I can't check and none of my family have commented on it, even before addition of the ND2, so I assume we're all immune from it.