Your GPU is passively cooled, SSD instead of a mechanical drive. Both of these will keep the noise down. the noisest part will be the stock fan on your CPU and your PSU.
Just done a little research for you and this PSU:
Corsair Builder Series CX 430W Is a solid, quiet PSU. and only £38.
As far as CPU noise goes your case has a 147mm height so large CPU coolers are out.
If you wanted to reduce the noise even more then this would fit in and be quieter than the stock CPU fan:
Scythe Shuriken Rev.B Quiet Low Profile CPU Cooler
As edgfactor said your CPU isn't going to really limit you over the next 4 yrs. Quad would make doubley certain but the dual core BE's are still perfect for the job.
SO:
Product Name Qty Price Line Total
Antec Fusion Remote HTPC Case - Black £138.88
(£115.73) £138.88
(£115.73)
OCZ Vertex 2E 60GB 2.5" SATA-II Solid State Hard Drive (OCZSSD2-2VTXE60G) £95.99
(£79.99) £95.99
(£79.99)
AMD Phenom II X2 Dual Core 555 3.20GHz Black Edition (Socket AM3) - Retail £71.99
(£59.99) £71.99
(£59.99)
Gigabyte GA-880GM-UD2H AMD 880G (Socket AM3) microATX DDR3 Motherboard £59.99
(£49.99) £59.99
(£49.99)
Samsung SH-B123L/BSBP 12x BluRay ROM DVDRW DL & RAM Lightscribe SATAII Optical Drive - Retail Black £47.99
(£39.99) £47.99
(£39.99)
Corsair Builder Series CX 430W ATX Power Supply (CMPSU-430CXUK) £38.99
(£32.49) £38.99
(£32.49)
Corsair XMS3 4GB (2x2GB) DDR3 PC3-12800C9 1600MHz Dual Channel Kit (CMX4GX3M2A1600C9) £35.99
(£29.99) £35.99
(£29.99)
XFX ATI Radeon HD 5450 SILENT 512MB GDDR3 PCI-Express Low Profile Graphics Card £29.99
(£24.99) £29.99
(£24.99)
Scythe Shuriken Rev.B Quiet Low Profile CPU Cooler (Socket 939/940/AM2/AM2+/AM3/LGA775/LGA1155/LGA1156/LGA1366) £25.52
(£21.27) £25.52
(£21.27)
Sub Total : £454.43
Shipping cost assumes delivery to UK Mainland with:
DPD Next Day Parcel
(This can be changed during checkout) Shipping : £12.50
VAT is being charged at 20.00% VAT : £93.39
Total : £560.32