I've a Virgin 80Mbps internet connection. With cable it goes usually up to 60-70mbps (using a speed test). But my wireless router caps it at 25-30Mbps. Also speed greatly degrades with distance. What kind of router is good enough to achieve full speed? If you don't want to recommend models, maybe list a set of features
Wifi speed may be influenced by a number of factors unrelated to pcs, and possibly even by electronics. Such factors include interference from other in-house devices like cordless phones, or nearby wifi networks. Plumbing (it may screen electromagnetic signals, just like a Faraday cage) or wall thickness also may lead to serious degradation of wifi signal.
In other words, you my get much less than the nominal operational speeds for the circuitry you bought. Still, you must make sure that you have material compatible with either of the following two IEEE directives, 802.11n or (better still) 802.11ac. 802.11a/b/g will not allow you to extract the highest speed of your cable connection, because they are limited to slower speeds (the fastest of this, 802.11g, caps at 54Mb/s).
So you must make sure that both the transmitting station (generally the router or modem) and the receiving station (generally, the pcs in your LAN) are 802.11n/ac-compatible. Also, you must make sure that, in the wifi configuration panel of your router/modem, you have chosen either 802.11n/ac, or the Mixed mode of operation (Mixed retains compatibility with older hardware).
If your ISP-supplied router/modem is not 802.11n/ac-compatible, do not worry. Just buy a router which is 802.11n/ac compatible, connect it to your ISP-supplied router/modem, and use the wifi network of your new router, after having disabled that provided by your ISP-supplied router/modem.