Well, since i've seen so many people complaining that there routers are not able to give 20Mb/s out effectively (many are reporting slow speeds with them in place) i decided to test the one i had simply laying around.
Enter: Linksys WRT54Gv5. Which i flashed a while ago with DD-WRT Micro from
http://www.dd-wrt.com
I set my Pc's up so one would act as a server (connected to the WAN port on the WRT54G, so the router will think it's the "internet") and i set the other up as a normal Client Pc, which your average home user will be doing.
I set the router a static IP address, so it didn't go looking for one from my "server" pc. Then i proceeded to host a temporary web server on this pc and host a nice 700Mb file as a test.
I tried downloading the file from the client PC with one or two applications, seeing what performance i could get out of it.
With IE7 i managed to get a decent 2.87 - 3.05MB/s constantly, fluctuating slightly as the data was written to disc. This works out as between 22.96Mb/s and 24.4Mb/s, which isn't bad. It passes the 20Mb mark easily.
Next application to test was Firefox v2.0.0.3. This has undergone no tweaking with fasterfox or anything, it's just a basic install. I achieved a massive 2911KB/s - 3.5MB/s (3525KB/s to be precise) which again fluctuated as the data was written to isc (It's an old pc

) This works out as being between 22.74Mb/s and 28Mb/s, which both pass the 20Mb mark.
So far, the router looks like it's passing, albeit barely.
The next thing was to test it loaded with more than a single connection, to get the most out of the router, and this is where it shone...
Using DownThemAll for Firefox was my next point of call, installed as an extension this handy little multi-threaded download manager proceeded to download using 1 thread (1 connection) at the usual 2.93MB/s, which is 23.4Mb/s. (Also passing the 20Mb mark easily)
Now, using 7 threads, as i normally have it set to, something rather nice happened. 5.19MB/s was acheived for a while, only slowing down as the data was written to the disk, yet again. Still, 5.19MB/s is decent performance and is 41.52Mb, which is DOUBLE the 20Mb barrier we were looking to break.
Maxing out DownThemAll with 10 threads on the same download (10 connections to one file) brought amazing results for spurts of speed i've not witnessed before now. I managed to hit a sustained speed of 9.94MB/s for about 10 seconds, before it slowed down once again, to flush the data to the disk. Now, this is an amazing 79.52Mb/s, which is almost 4x the 20Mb/s connection VM are offering.
In short, this router is capable of 20Mb/s. But to really see it shine, use a download manager. This router is capable of upto 80Mb/s, as it should be with it's 100Mb WAN port.
I'd highly recommend this router.
On a side note, this router is actually for sale as i'm no longer going to be on cable.