OK, then that means your maximum possible throughput is about 1.25MB/s on
the WAN side, and you MIGHT need about 1.5MB/s or greater on the WAN side.
Interesting.
Well I still don't know if it's worth an upgrade, as even AT WORST your
current router isn't going to slow you down much, and that's assuming that
your 15mb cable modem is running at it's theoretical maximum throughput
(somewhat unlikely). In other words, have you run speed tests using JUST
the cable modem and a fast NIC???
If you're not REGULARLY exceeding 1000KB/s (or 10000kbps) download speed,
then your router is not a bottleneck at all. Keep in mind that actual data
throughput is about 1/10th of connection speed. So your
theoretical -maximum- download speed is about 15000kbps, but you aren't
likely to hit that on a regular basis. Try broadbandreports.com for speed
tests.
If your speed tests (a few a day, for a few days) exceed 10000kbps, then
maybe a netgear WGR614 is in order. That one has 10/100 on the WAN side
(and the LAN side), so it should offer you plenty of breathing room for the
foreseeable future. I use two of them myself, and they work great.
You don't necessarily need the wireless function, but the last one I bought
was only thirty bucks, so I doubt if you could buy a non-wireless one for
much cheaper.

-Dave