If you are looking for a world of pain and challenge with failure being the most likely option then go for it. Haveing the GVP will help you get there quicker.
Once you have a tcpip stack with a gateway defined you will be able to FTP and HTTP(Browse) to the internet using your adsl. As long as you can fit everything in 10Mb.
A network card might be a challenge though..Thus the tutorial use of serial and a modem..
Good luck...!
You can easily fit TCP/IP, an IRC Client, and possibly IBrowse (without too many tabs open) inside 10MB... (You can fit Miami and AmIRC inside 2MB - I tried it on WinUAE...)
I'd say having the extra memory makes this possible, the only issue is what to connect your Amiga via... on my A1200 I use Wifi through the PCMCIA port, i'm guessing on the A1200 it will be the serial port... but how do you configure the serial to connect on the Windows/Linux/Host side?
But yeah, it definitely is possible.
Alex.