You will need to be able to access the Slipstream's setup/config interface and either print or write down all the config info for your ISP...either that you will need to call your ISP to get them. Sounds like your ISP is difficult at best...if you don't know how to access the Slipstream config here is info on how-to:

http://www.dslreports.com/forum/remark,12998125

There is another option and that is connecting a wifi Access Point to your existing router. It might be easier then a whole new router/modem device. You can just wire in the AP to one of the ethernet ports on the Slipstream config the AP via the mfg's instructions and viola it's done. But the Slipstream might not like the AP though it should be OK.

Plus the AP will be a lot cheaper then the all-in-one device if cost is a factor.

EDIT: You might also be able to use the current Siemens as just a DSL modem and connect it directly to a basic wifi router's WAN port. I am not sure of the operations modes on the 4200 but it's not impossible to imagine you can turn off the LAN side of the device and use it in "modem only" mode. If this works you can pickup a Linksys wrt54g for under $50 and after just some quick changes to the config/setup it's done vs. at least $150 for an all-in-one.

Here is a wrt54g at WallyWorld:

http://www.walmart.com/catalog/produ...uct_id=2470125

BTW the device in the OP will not work for what you want...