That's just it. No big budget. There's 4 cameras on an 8 channel capable system. Three out of the 4 cameras really don't have that good of a picture. There's 1 that has a pretty good resolution.
I'm not changing to a new system or ditching the dvr. My question is simply what are the best cameras to look for with this system. There's a whole host of possibilities for a low price on Ebay. No, they aren't the best, but they're pretty cheap. I'm looking for the best I can get with the existing system. I just want to be sure I don't get something that's incompatible.