TiVo Roamio and a CableCARD (and Tuning Adapter) from Cox is what you want. Try it for 30 days and see for yourself.
https://www.tivo.com/shop/roamio
You pay one price for the Hardware (DVR) - 4 or 6 Tuners
And you also pay TiVo monthly for service - $14.99/mo or get Lifetime for $400 if you use the PLSR code when activating. Otherwise the 1st TiVo DVR is $500 for Lifetime service.
I suggest you purchase at Amazon or get BestBuy to price match Amazon, If after 30 days you do not aggre cancel and take it back, I think you will be sold.
You can easily upgrade the HDD to 3TB, by simply replacing it with a new HDD and rebooting
TiVo Roamio 4 Tuner - 500GB 75Hrs HD - upgradable to 3TB
http://www.amazon.com/TiVo-Digital-Recorder-Streaming-TCD846500/dp/B00EEOSZK0
TiVo Roamio Plus (w/ built in Stream & MoCA) 6 Tuner - 1TB, 150 Hr HD - upgradable to 3TB
TiVo Roamio Pro (w/ built in Stream & MoCA) 6 Tuner - 3TB, 450Hrs HD