Currently I'm using a SSD drive as my boot up drive & have a couple of 1 TB HDDs daisy chained. Since I updated to the Win 64 bit OS, I have been considering getting a new 3TB or 4TB HDD to replace all my older 1TB drives. Probably save some electricity if I run just 1 HDD.
Which brand & capacity should I look at
The following are some of the current prices of HDDs:
Hitachi Enterprise (warranty 5Yrs) 2TB $210
HGST NAS 7200rpm (warranty 3Yrs) 3TB $179
WD Black 7200rpm (5Yrs) 2TB $185
WD Black 7200rpm (5Yrs) 3TB $237
WD Red Pro 7200rpm (5Yr) 2TB $198
WD Red Pro 7200rpm (5Yr) 3TB $238
WD 6TB Caviar Green 64MB (2+1 Yr).......338
WD 4TB Caviar RED NAS HDD (3 Yrs)......235
WD 6TB Caviar RED NAS HDD (3 Yrs)......375
WD 4TB Caviar Red Pro 7200rpm/64MB (5Yr)...318
WD 4TB Caviar Black 7200rpm 64MB (5 Yrs)...310
Which brand & capacity should I look at

The following are some of the current prices of HDDs:
Hitachi Enterprise (warranty 5Yrs) 2TB $210
HGST NAS 7200rpm (warranty 3Yrs) 3TB $179
WD Black 7200rpm (5Yrs) 2TB $185
WD Black 7200rpm (5Yrs) 3TB $237
WD Red Pro 7200rpm (5Yr) 2TB $198
WD Red Pro 7200rpm (5Yr) 3TB $238
WD 6TB Caviar Green 64MB (2+1 Yr).......338
WD 4TB Caviar RED NAS HDD (3 Yrs)......235
WD 6TB Caviar RED NAS HDD (3 Yrs)......375
WD 4TB Caviar Red Pro 7200rpm/64MB (5Yr)...318
WD 4TB Caviar Black 7200rpm 64MB (5 Yrs)...310