Hello, according to the problem you described, I can figure out that it's quite probably a problem of DSP. What type of DSP does your DVR applied? As you know, DSP is the most important part of a DVR, and it's also where the cost of a DVR lies. At present, Philips DSP and Texas Instruments DSP are two most popular ones. Our DVR applies Philips DSP.
TM8804C(4 channel CIF DVR/120/100fps at 360*288) might satisfy your cost requirements. You can access our dvr through the link in the subject. The password is 888, pls have a try to have an evaluation about the image.
Hope to receive your reply.
Jasmine