Platform i386:

I'm thinking about getting @home and keeping my DSL connection.
I hadn't really concerned myself with exactly how this would work,
I just assumed it could be done.  Recently in a news group I read
a post from someone running FreeBSD.  He was having trouble getting
incoming traffic on his cable modem to go back out on the cable 
modem.  This immediately made sense (I think?) because his default 
route is his other connection all out bound traffic will go out that 
connection.  

I think I can solve this by having the cable traffic NAT'd into
a subnet, say 172.16.1.0/24. The subnet can be routed back to the 
cable modem's DHCP assigned address.  I was also planning on NAT'ng 
http & ftp requests out the cable modem (assuming it performs better
than the DSL line, which isn't clear from reading the cable modem news
group).

The traffic from my DSL connection is just distributed to my assigned 
CIDR block. And will be default routed.

Am I being to simplistic in my method?  

I'd appreciate suggestions, alternatives and/or things to look 
out for?

TIA,
Paul