Internet Bandwidth and remote access

Hi,

I have a 2MBPS leased line at my company's site and some of my users connect
to our LAN over the internet using MS Windows VPN Server (2003). I also
connect to our network using the VPN over my residential broadband line
(cable modem, 4MBPS). I find that often when I try to open files, etc. over
the VPN connection there is quite a lot of drag (performance with respect to
speed is poor). When I have mentioned this to my ISP and they have reported
that the maximum bandwidth used in and out of our internet gateway is 1.3
MBPS and it averages about 50KBPS and so there shouldn't be a need to up my
internet bandwidth. However, I have noticed that when I used to download
something from MS, for example, on my old 1MBPS residential line I used to
get a certain speed (+/- 100KBPS), and when I doubled my bandwidth so the
download speed doubled (+/- 220KBPS). Now I do know that there are several
things to factor in when working out why the speed of a download is what it
is, but what I am trying to clarify is this: If I use on average 50KBPS and
double my bandwidth would I notice a performance increase with respect to
download and upload speed? I would have thought the answer would be yes,
but I would like to make sure be for I open my mouth, if you know what I
mean? Surely even if I only use a certain amount on average that means
something, but by upping the bandwidth on my leased line the speed into my
network for remote users is going to be greater, and therefore better, isn't
it?

TIA,

Jarryd