The 54Mb/s rating of the wireless side of the router is only for wireless. The ethernet speeds you should expect would be 10Mb/s, (Very Old), 100Mb/s, (old), or 1Gb/s ("New") so it should be possible to achieve throughput in excess of 50Mb/s with your existing kit. Of course this assumes that you do have 100Mb/s ports on the router, and on the computers, which would be expected (applies to one computer ethernet connected to the router, shared access will reduce the actual bandwidth of all devices).
One thing you have to be aware of is that very few ISPs serve the "headline" bandwidth they quote - some can say Up TO 100Mb/s and it only Ever get's Up To 50 50Mb/s especially at busy times