PCI is largely becoming a legacy expansion slot, much like AGP and ISA. However, there are still a large number of PCI devices available (both through retailers, and around many households) so I try to buy motherboards with at least one PCI slot. Most PCI devices can be found in PCI-E versions now, though, like Creative's X-Fi sound cards.
On the other hand, only you can answer whether or not two PCI-E x1 slots will be enough. You have to consider what expansion cards you may need in the future - sound card, RAID card, USB 3.0 card, etc. As far as I know, any PCI-E x1 device can also be used in a full-sized PCI-E x16 (or x8) slot as well, though it may cause other PCI-E x16 slots to drop in speed (such as x16 -> x8 + x8).