Venomous, ISA modems are generally better and also cheaper than PCI modems. ISA NIC cards are up in the air- 10/100 NICs are generally hard to find for ISA but 10Mbit ISA NICs are cool if you are just on a 10Mbit hub or something.
Also, why does it bother you SOOOO much that there are ISA slots on motherboards? You don't want to use it- don't! I really can't imagine you need that 6th PCI slot. Heh, 5 PCI slots often result in IRQ problems so that 6th PCI slot is chancy anyway.
All that taking off that ISA slot does is allow manufacturers to put a 6th PCI slot on and cause people with kickass ISA modems to have to dish out more money for a PCI modem.
Now, this problem doesn't affect me because I use a PCI NIC for my cable modem, but it does affect others.
