phishphreek,

Every router where access-lists (since i know you have a cisco ) will do a lookup to get the ip. It's just a matter of putting a good access-list. I know you can even allow certain dns'es so that would solve your probs for sure.
And besides I don't think you would notice the difference with or without the router doing lookups.

I would surely at least try it for a week or so, since you are always able to reset to your old values. This really seems the easiest and the cleanest way to do, so surely worth a shot.

Besides just read your edit, Have it a go and if you need me you know where to find me on irc.

Cheers