Well, Neem's suggestion will work, but on a home router it's certainly not going to be optimal.

I think you'd be better server by buying a 2nd wireless router, and hook
PC-#A to your old router, and
PC-#B to your new router; both Wi-Fi connected. Otherwise, you'll have contention and beaconing on your Ethernet connection between the 2 PC's, even if on separate subnets!

You're PC on each subnet/wireless connection to your router will be fighting sending/receiving Ethernet packets between the NIC and the WLAN (internal or external Wi-Fi card/adapter). This is NO-BUENO!
This method will also effectively cut your Internet speed or bandwidth in half, since 50% of the wireless signal must be divided between 2 subnets, each with 1 PC on it. It will work, but I believe it's not going to give you the performance boost you are looking for. To do it right, you should get a Cisco 2600 or 3500 industrial router which has subnet fast-Ethernet switching and can handle a direct-link between PCs on different subnets through a mechanism known as
LOAD-BALANCING. Home routers do
NOT have this feature (MIMO is sort of poor-man's Load Balancing). Cost of these routers is from about
$2,500-$6,000 US. This is pretty pricey to really fix your problem. You could also pick up these routers used on ebay for a fraction of the price; say about
$500-$800 US or so.
Using those devices requires advanced networking skills; and if you decide to do that, you should consider hiring a Cisco-Certified
CCNA or
CCIE Engineer conversant in Cisco IOS (the Cisco OS)to design and install it for you. Pricewise, you are looking at several hundred dollars to several thousand for one of these experts to put in this equipment in your home.


[Labor Cost alone]. I have done so for several Clients over the years.
Just food for thought.
<<<<<BIGBEARJEDI>>>>>