You have got some rather antiquated bits hanging off that network, though they are still ok for a reasonable, if not blistering, connection.
Consider these points:
- How fast is your ADSL connection?
- How many concurrent connections to your ADSL do you actualy use?
- Do you move a lot of bytes internally around your network?
These questions and more will be answered in next weeks edition of SOAP! (sorry, 80's flashback there - back to business).
First off - yes, update the NIC in the desktop. Go for a gigabit card, they are cheap as chips these days and should be good for a few years yet.. I prefer to go for better knoen brands than unbranded Chinese specials - most of those unbranded cards are good, but the odd one can cause problems. I tend to go for Netgear onboard cards myself.
Definitely wire the desktop if at all possible - much more reliable and faster connections.
The router looks pretty good for your needs, though personally I am a little shy of 802.11n, there are too many flavours at the moment (although that said, it's been like that for a few years now), so there could be compatability issue firther down the line.
Wherever possible, I go for PCMCIA wireless adapters for laptops, they are considerably quicker and more reliable than USB variants.
All the above will meet your needs for downloading and file sharing within the house.
you are of course downloading for kosher reasons, no music/video ripping of course!