If your laptop has a N nic card then it would help to get an N router.They are all backward compatible to B and G also.
I too have Comcast and was using the same router you have.
I upgraded my speed and had to buy a SB6120 DOCSIS 3.0 modem for the speed tier I am on.
I tried using my laptop with the old Linksys router and could not get near the speed I should. My laptop has a N nic card so I bought a Netgear 3500 N router and my laptop speeds more than doubled. Not only the speed but the distance from the router has increased considerably with a 5 bar signal.
So I guess it depends on on what NIC card is in your laptop.
I don't know about the ipad wifi and how that works.
A word of caution, If you do get a N router stay away from Linksys. I had two of them before the Netgear and had to take them both back because I was having to re-boot them every day or the speed would go down to almost dial up speeds.
I have had the Netgear for 6 weeks without any problems.
I have an HP Slimline s3700y, with 2.60 GHz dual core processor, 3.00 GB RAM and running Windows 7 Home Premium (32-bit). My desktop is hard-wired to internet through Comcast high speed modem (DPC3000), which I just checked for connection speed (download 35.55 Mbps / upload 6.43 Mbps). I'm currently using a 5-year old WRT54G v5 Linksys wireless router (802.11g) for my home network which I use only for peripherals (laptop).
My question is whether or not I need to upgrade my router? Would this improve wireless internet connection for my laptop. I've also got an iPad(WiFi) on the way. Is my current router sufficient for this device?