I've been using a dual-monitor setup for ages - once used you'll never go back to a single!
Matrox make LOVELY dual and triple (and more!) cards. I have a P650 and G450. As amanoffewwords says, they're not suitable for really high-end gaming but are perfect otherwise. Very very accurate colour and the secondary screen is as sharp as the primary (not always true).
Alas, both cards are now languishing since Matrox can't be bothered to produce proper Linux drivers. I replaced the P650 with a Chaintech nVidia 6600GT which performs very well all round and feeds the secondary monitor thru a DVI socket and adapter.
PS: Why are you going for LCDs? If you don't mind the extra space and power consumption CRTs still have a much better picture and are considerably better value for money.
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"Bother," said Pooh as he struggled with /etc/sendmail.cf, "it never does quite what I want. I wish Christopher Robin was here."