Need an inexpensive RAID solution

Hello. I am new here so I hope I am not posting in wrong forum or breaking any rules.

I need an advice from you. I am video editor and my main work is done on workstation, lately I've been freelancing a bit and I need to adjust to that a bit at home.

My situation is kind of weird now, I am running on a backup computer which is actually 2011 MacBook Air (11", i5, 128 GB SSD), it's not a great machine but I'm waiting for new Mac mini to come out. I am probably what you would call "prosumer" although I do earn living from video editing.

The computer does OK job at editing HD videos and doing some simple stuff in AE but my main problem now is storage. Internal SSD on MBA is only 128GB and my only other external drive is old WD MyBook connected via USB 2.0.

That connection is painfully slow because I use it as my scratchdisk (my internal SSD is full), especially with HD videos. I've been thinking about getting Thunderbolt solution because my new Mac will probably have TB port as well, that means I could utilize it in future as well.

My needs are:
- fast reading times of 1080P videos
- drive redundancy
- at least 1TB of space

I am not expert at storage solutions but I guess something with four drives would be nice? Like setting up RAID 0+1? Or Maybe RAID 5 (but from what I gather it cripples write speeds).
I am somewhat undecided when looking at current TB offerings and the only solution I'd consider is Promise R4 which is a bit more than I'd like to pay but if it can get the job done without much hassle I'd probably take it.
G-Tech Thunderbolt G-RAID is less expensive but has only two drives (and when I'd purchase another unit in the future for adding another array I'd get over the price of R4).

Maybe I'm just overthinking this whole thing and for person like me FW800 drive would suffice (it'd be possible when now the TB-FW800 adapter is available). I know I can't RAID firewire drives (maybe using software RAID, but that slows thinks down, doesn't it?)

I'd like to hear your opinions.

Thank you very much for your insights.

OK I'll go with Thunderbolt, I can utilise it definitely in few years to come. I am still deciding though..
What do you think about WD MyBook Thunderbolt Duo? It's around 40% cheaper than Promise R4, the only downside is that it's only 2 bay.
I was thinking I could scale it up as time goes, start with one unit in RAID0 or 1 and chain it later with another unit and add it to array. My only worries are:
- Is it possible to create hardware RAID among two units? For example if I had one Duo in RAID0 and I added later second Duo, can I set it up as RAID1 or RAID5 natively? Don't know if there is such support and I didn't find answer anywhere.
- Once I add second unit (and price of cables), I'm over the price of Promise R4 by around 20%. This is probably for me to decide, just wanted an opinion on it.

Yeah you're right, I did some reading here: http://www.tomshardware.com/reviews/my-book-thunderbolt-duo-pegasus-r4-2big...

I'd be better off with R4 in the long run, I'll just bite the dust and get it, even though it's a bit more than I wanted to spend, eventually I'll be happier with it.

Thanks for insight.

Bob - if you gang these together, can you multiply the read write speeds? or just increase storage? I used to use sonnet and when ganged up could double the speed with each box

A long term DP - likes 35mm and HD equally - changing with digital media - Began as a commercials editor !