hello , i am thinking of buying a cctv dvr system , ive seen a few on ebay , 8 channel one with 500gb hard drive , some are with the cameras , some arent , just wanted to know what are the best cameras to get , ive been looking at these, http://www.ebay.co.uk/itm/SANNCE-4-Black-Bullet-800TVL-Outdoor-42-IR-Cut-Security-Surveillance-CCTV-Camera-/111508734280?pt=UK_CCTV&hash=item19f6704148 , any help /advice would would be appreciated thank you