Newbie question - RCN and TIVO - need more space

I live in NYC and have RCN with a basic DVR right now that saves about 45 hours of HD of shows. Its not enough for me. I only need one device. RCN said my only option is a TIVO rental for 17.95 a month for the quad or I can buy a TIVO on my own but there is a monthly fee from TIVO of 14.95.



Does anyone have any suggestions for me? I really dont want to spend 17.95 a month for a rental of a DVR just to get 30 more hours of space. Any other options?