One question you need to figure out is: stand alone Tivo or DirecTivo?
Stand alone can be treated as a VCR. You can also find Tivos w/ the DVD, as you've mentioned. These are good options, but as you'll see w/ DirecTV, the combo unit is much more powerful.
I have the DirecTivo unit. Has 2 DirecTV tuner so that you can record 2 shows simultaneously and then watch a 3rd previously recorded show. Why is this important? (Since you like tennis, if I remember correctly...) Let's say Wimbledon is on at the same time as the Summer Olympics men's singles finals. W/ DirecTivo combo box, you can watch both. Watch Wimbledon, when a commercial is on, pause. Flip to Olympics, when commerical is on, pause and flip back to Wimbledon and FF thru commercials. AWESOME! No more commercials. You can't do this w/ the standalone because it only records one input. Also, the combo box records in native format, so there is no compression when it's recorded. The next (and much bigger step), is to belly up to the HD DirecTivo w/ 2 DirecTV tuners (HD) and 2 over the air tuners. The Tivo Holy Grail... This is out now, but expensive at $999 MSRP. The key here is if you are willing to go DirecTV. If not, then standalone is your option. DirecTV's been running deals for new subscribers to get the Tivo and DirecTV for $49 or $99 depending on who you go w/.
For either Tivo, you can get upgrades for bigger hard drives at weakknees.com or 9thtee.com. I have a 120GB drive on my for 110 hours, great for summer when all the reruns are on and I can catch up on Sopranos, 24, and Deadwood. AND, if I can get a discount on HD DirecTivo this weekend, my existing DirecTivo will be for sale soon...
