Help antenna and cable

Hi Guys so here is my issue:

I have a WRT54G v6 router and I am trying to get higher speeds from a wireless network, I have set up a dish and a cantenna and is going really well about 18-22dbi gain which is very noticeable but I have a question, does an Ethernet cable speeds up the transfers? like a high speed cat7 cable that can transfer data at much higher frequencies, Will that help? or the router can't handle it?.Also another question is how can I make the gain on the dish higher?