[spydertau]

The archetype has several different comlinks with different ratings than the default ones, however, I can't find the rules on how to increase the ratings at character gen with build points.

[Wyldknight]

Increasing the ratings on the comlink is done with money. They have the prices listed.

[Glyph]

In the basic SR4 book, hardware upgrade costs are on page 240 (*edit* don't have the page number for SR4A, sorry).  You get System and Firewall at different ratings by buying them as separate programs instead of using one of the stock operating systems.

[SpikedWheel]

In SR4A the costs for hardware upgrades (Signal and Response) are on page 322.  Software upgrades (System and Firewall) are on page 330.

Personally, I always buy up Firewall as high as it'll go.    :p

[Lansdren]

be aware that if you do some upgrades on your own gear it can only go up by +2 Response and Signal from the stock level of the link.