My sister is in need for some professional data storage

I need some ideas for mass local data storage.

My sister is a professional photographer and with multiple 10-12MP cameras the size her photo archive grows insanely fast.
She might come back with 3-5GB of pictures from a single job.
And everything needs to be archived for future use/purchases.
These pictures are her life, so secure data storage is a must.

Right now this is her current HDD setup:
3x 320GB Seagate 7200.10 in AMS Venus External Case
1x 500GB Seagate 7200.10 in AMS Venus External Case
1x 500GB WD MyBook
1x 500GB Seagate 7200.10 Internal
1x 160GB Maxtor Internal for OS/Programs

And a 750GB Seagate 7200.10 on the way.

She's pretty good at keeping everything backed up on DVD, but still single drive and only DVD backup for such important/mass files is just DEATH.
I've been telling her for years she needs some kind of professional storage/hardware RAID file server with remote backup but she hasn't wanted to spend the money on it. I'm going to force her to do it now though because its getting out of hand.

We've done software RAID from the motherboard/controller card in the past when her archive was smaller, but that was a headache to begin with and now its just much too large for that, and expands too fast.

Need some type dedicated NAS with hardware RAID thats expandable / hot swappable. Connected to her desktop by fiber/gigabit/firewire something.
With some type of remote backup.

So I need some ideas from you guys that have experience in this. Needs to be cost effective and expandable.
Thanks

My suggestion would be similar to what I've just done... I picked up an old server box and custom-made my own drive mounting system that will take 8 3.5" drives, plus a 3ware 8-port card. So far I've got 4 x 500Gb drives in Raid5 (1.3ishTb). Leaves me room for another 4, which will be over 2.5Tb in the end. No problems changing motherboards as they rely on the card, and being hardware raid, a more reliable setup.

I'm still setting it up and getting it to how I want it to be, but for what she's doing... that plus a BBU on the card and you'd be away. Hell, it doesn't even have to be a server... just a PC and a cheap one in a big case at that. I think there's even a pretty Stacker case for sale atm.

I just put together a storage solution for my uncle who does video editing.
The situation is different because I was just building a very fast 1 terabyte raid for his working set.

I didn't find any problems with the intel ICH9R raid setup. It's not hardware raid, but its 100x cheaper. OS level software raid wouldn't be too bad either, if you are running *nix.

If I was going to build a NAS I would get a motherboard with as many sata connections as possible and gigabit ethernet, fill it up with drives and run software RAID 5 and BSD or Linux with Samba.
All the other hardware can be dirt cheap, celeron with 512mb of ram sort of deal.

If that sounds like too much trouble there are plenty of NAS enclosures on the egg, read some reviews. It will cost more but take up less space and use less power.