Pretty much all newer TVs that have an ATSC tuner also do clearQAM, even if it's not listed in the manual (mine is one of them, it makes no mention of clearQAM but receives it fine). So I would just hook the cable up to the TV's tuner and do a scan to see what happens. Then it's there if you need it, but you'll just have to flip to the tuner input. Only downside is you won't get the guide integration.
Just be aware though, when you order just cable internet without video service, standard practice is to install a video trap on the line so you don't get 'free basic'. This trap is non discriminating, it catches everything - including the 'free and clear' channels. So while video trapping is often a 'neglected' step in the cable modem install, don't be surprised if you get nothing but snow..