You need to connect the 2 DVRs to the Comcast router using 1 of two methods:

1) Wireless connection
2) Wired connection

With the wired connection, you'll run Cat5e or Cat6 through/under/around your house to your router. You'll want wall plates w. the appropriate jacks. This often is a reasonable DIY project.

For wireless, you'll want to get 2 wireless access points and a wireless router (if the comcast router is not already wireless). Each DVR will connect locally to an access point. The access points will then connect wirelessly to the router. I would suggest Linksys or D-link as good brands. You can expect to spend ~$300 for two N-band access points and a router if you buy new. Comcast may swap out your router to a wireless one for free if you ask (especially if you mention that you want to spend $$$ on their OnDemand & PPV services).

The wireless option will be more expensive in terms of hardware but should be fairly painless.

Curious, how come you pay for both DirecTV and Comcast? That's two programming providers in one household. I would think you could get a better value by bundling up one way or the other.

Given what you have, I'd suggest you wire a connection. Run a Cat-5 line. Simple for someone who does that for a living, but you might need a crimper to put some ends on. If you don't have a crimper or do that sort of stuff then get a 100' or 50' length with ends on it and you're home free.

Even if you change out providers later, having a cat-5 run from your router area to your TV area will come in handy. I have U-verse, and they don't even use cable any more. Just cat-5 right from their router to your cat-5 cable box -- it's neat.

I would run a couple while you're at it. You might need one for a Console Game, TV, Cable Box, Computer, or anything else you want to connect to the internet in that area later.