You will not get any better picture quality from a Series 2 since its analog and HDTV is digital and analog is only through the Y/W/R. With Series 3 and older, including Premiere, which has HDMI, they are digital capable. Series 3 can go up to 1080i resolution, and Premiere to 1080p.
Original S1 (Recycle Heaven)
Series 2 (PLS, sold)
TiVo HD (XL, PLS, "652")
Juliet Basic (4XL, PLS)
The TiVo Apocalypse begins on Sat 2013 Feb 16 00:00 GMT!