...does my new i7 920 DAW (Digital Audio Workstation) build look a-ok?

I have heard Crucial is doing better with DDR3 i7 memory, but I still don't trust them after the mess they made with the DDR2 over the last year or two. Crucial would probably be my last choice.

I suggest you get the Corsair 650TX instead. I think quiet is more important than modular in your build.
Ref: http://www.silentpcreview.com/article699-page1.html

Here is another choice:
http://www.ebuyer.com/product/144085
Modular and very quiet... You mentioned the 620HXEU so I guess you are in EU somewhere  

hmm, i do not know a thing about Crucial's past. i haven't been PC-shopping for years now and am totally inadequate actually, but my googling skills have got me thus far. what memory would you recommend instead then? is there anything better that doesn't cost twice as muchl?

about Corsair, the place i was intending to buy the build at has the CORSAIR 620HXEU (620w 120mm fan atx eps12v) and next up from that is the CORSAIR 750TXEU (750w 140mm fan atx), no 650TX in between. would it be worth the trouble of finding another place that sells the 650TX or would one of those be good? (i read here that the 750TX would make more noise under load than the 620HX though.)

Check out these DDR3 Triple channel Ram, you want to go with Cas7 or Cas8.
OCZ 6Gb (3x2GB) DDR3 1333MHz Memory CL7(7-7-7-20)
http://www.ebuyer.com/product/152747

OCZ 6GB (3x2GB) DDR3 1600MHz Triple Channel Memory Kit for i7 Motherboards CL8 1.65V
http://www.ebuyer.com/product/158392

Some other good 1366 mobo for you to take a look at that OC very nicely.
Asus P6T, Intel X58 £161.20 Inc VAT
http://www.scan.co.uk/Products/Asus-P6T-Intel-X58-S1366...(x16)-Triple-DDR3-2000(OC)-SATA-3Gb-s-SATA-RAID-ATX

Would suggest this 1TB HDD over your selection mainly due that the one you selected will slow down rpm.
Western Digital WD1001FALS 1TB Black Hard Drive SATAII 7200rpm 32MB Cache £65.99inc vat Free Delivery http://www.dabs.com/products/western-digital-1tb-caviar...

Would go with the Corsair 750w PSU, mainly due to upgradable for future needs. Comparing the price between the two below.
Corsair 620W HX Modular PSU - ATX12V v2.2 APFC £89.84 inc vat Free Delivery
http://www.ebuyer.com/product/114941

Corsair 750W TX PSU - 120mm Fan, 80+% Efficiency, Single +12V Rail £89.99 inc vat Free Delivery
http://www.ebuyer.com/product/134677

Would also suggest one of these Cases with Free Shipping @ eBuyer.
Coolermaster HAF 922 Mid Tower Case £89.52inc vat
CM Storm Scout Case - 120mm and 2x 140mm Fans Included £74.97inc vat
Antec 900 Nine Hundred - Gaming Case with 200mm Top Fan £74.98inc vat
Antec 902 Nine Hundred Two Black ATX Case £85.99inc vat

I would get one of these CPU Coolers'
Titan TTC-NK85TZ Fenrir CPU Cooler £29.99 inc VAT
http://www.overclockers.co.uk/showproduct.php?prodid=HS...

Cogage True Spirit £32.19 Inc VAT
http://www.scan.co.uk/Products/Cogage-True-Spirit-120mm...

One of the latest Reviews on 1366 CPU HSF Coolers'.
http://www.hardocp.com/article/2009/07/23/intel_core_i7...

I would suggest moving up to the 9400 to 9600 nvidia series card if you can.
http://www.ebuyer.com/search?page=1&store=2&cat=215&sub...

Also Links to more UK Online Computer Parts Stores
http://www.ebuyer.com/
http://www.overclockers.co.uk/
http://www.dabs.com/
http://www.scan.co.uk/

Yoosty, digital audio workstations need to be quiet.

The 750TX would not be a good choice due to noise, and any large PSU is not needed as this is not a gaming build.

The Noctua fans are quiet. You can mount two on the cooler and run them at half speed and you won't hear them at all.

Sethh, get the Corsair 650TX or the Enermax I linked. They will serve you well in the future as well. See the reference I provided for their silence ratings.

None of the cases Yoosty linked are truly quiet.

Here are two that are:
Antec Sonata
http://www.ebuyer.com/product/158602

Cooler Master Cosmos
http://www.ebuyer.com/product/132077