Hi, We're about upgrading our security system, and I would like to get some advises. I hope I came to the right place. today, we have security cameras with low res, so we want to replace them for an HD cameras. also, we'll probably 'll replace our DVR. So, first. Should we buy everything from the same security company, or could we choose whichever cameras and DVR we want? also, I would like to get some recommendation for a good DVR and cameras. we're talking about 10~15 cameras, indoor and outdoor. Thanks in advance. p.s. if you think this isn't the right place (or if you know a better place) for this topic, please point me to another. thank you.