The wire from the wall to the DSL 'modem' isn't that big of a deal. Use a good quality phone cable (if it's new service from ATT, the modem should have included a phone cable) and you'll be fine. Any wiring concerns you might ever deal with would be inside your wall wiring. If it's an old house, the wires inside the wall might cause some issues, but a previous thread talked about a home run from the NID to the wall jack for the DSL connection. That'd be a good idea. Be aware of florescent lights in the immediate area (don't put the modem directly under your desk lamp) but other than that, you'll be fine. Just remember, if it's anything other than Windows Vista, you'll need to tweak the RWIN and MTU settings to ensure getting the best speed and pings. Vista does this (sort of) on the fly and does not need tweaking. See here: http://www.dslreports.com/tweaks
Supposing I'm trading remote, which are the advantages in terms of performance of a fiber setup @ my LAN if my connection to my broker is via a 4Mbit/256k DSL line??
I meant a regular 100mb/1gb LAN with a fiber connection to your ISP. In the US, Verizon FiOS will give you fiber with something like 5mb up and 20mb down. It is not available for all areas yet but gaining in popularity. I assume other provider in various regions offer or will offer something similar soon.
Anyone of you are using cat 7 ethernet cables for better reliability (not simply in terms of faster speed needs allowed)?
If you are running a Cat 5e network and its not reliable (as in, error-free) then you need to pin-point the source of the problem; upgrading the cabling to the latest psuedo-spec is not the solution.