I always use Maxtor drives. They've never let me down. They do as they are supposed to do. That is all you can ask!!
As for the size of cache (buffer), I don't think Maxtor do one of less than 8MB in a 120GB drive.
I would go for Maxtor DiamondMax Plus9 120GB 8MB Cache - OEM (HD-013-MD) from click here
£73.90 ex VAT, £86.83 inc. VAT