If you check other posts on this Forum....you'll see MANY of us STRONGLY advise against a gateway device.....a separate modem and router is the most reliable way to go......
As for a "best" router......kinda like asking "Which is better....Ford or Chevy??" You'll likely get many different answers......If you stay with the major brands -- Linksys, D-Link, Netgear -- and try to steer clear of the least expensive in the line......you should do OK.......
At some point you might look into upgrading the 5101 to something like the SB6120/6121 or the Zoom 5341J....the latter 2 are DOCSIS 3.0 ready and provide "future-proofing" to your home network. Both allow multiple channel bonding, both up and downstream (the 5341J can provide 8 downstream and 4 upstream channels.....WHEN CC provisions this for your area.....).
Your wireless coverage will depend on the type of structure you live in.....a 2-story "stick-built" cape can have better overall coverage than, say, a steel and concrete apartment building. Try to get the router as high as possible....some models allow orientation of external antennae (fewer models offer this today.....)....try to keep the router away from other devices using 2.4 GHz technology (ie., cordless phones, wireless printers, etc.). Most models offer dual-band operation - in this case, you MIGHT fare better using the 5.8GHz frequency range...YMMV!!
Don't forget to power-cycle the modem if you insert a router between it and any PCs....And be SURE to check the "sticky" at the top of the forum page for Baric's instructions on securing your wireless network.
If you run into any problems, just check back....Someone will be able to walk you through most any issue you may encounter.....Good luck!
Along with the above information, you should stay away from any Linksys router until the company has issued a firmware upgrade to fix the WPS Brute Force Pin Vulnerability. Stay with Netgear, D-Link....
While I agree the current Linksys models suffer from this vulerability with not way to disable WPS, Linksys has announced that a firmware fix will be available in early March to address this. Personally, I would not let this stop me from buying a Linksys product, they are generally very well made.
Thanks for the advice. If I purchase the Zoom 5341J modem, specifically which router would you suggest I pair with it? My house is a two level (half brick/half siding) and the router will be downstairs where Comcast has the internet cable coming into my home.
My son has cancer (he's home-bound during treatment) and I really need the modem/router to work both upstairs and downstairs in the home so I'm prepared to pay whatever I need to pay for him to have the BEST COVERAGE and HIGHEST SPEEDS throughout the home!
You can use any router you wish, the cable modem doesn't effect that decision. Everything really depends on the exact constrution of your house, but in general, stick with the high performance routers designed for gaming or streaming HD video, like the Linksys E4200v2, the Netgear WNDR4500, Asus RT-N56U, etc. I normally say stick with the big names, but the Asus is really making a name for itself in routers with superior performance.