This

BACKUP DATABASE Test1

TO DISK = 'C:\temp\20130319_1.bak',

TO DISK = 'C:\temp\20130319_2.bak',

TO DISK = 'C:\temp\20130319_3.bak',

TO DISK = 'C:\temp\20130319_4.bak',

TO DISK = 'C:\temp\20130319_5.bak'

Should be this

BACKUP DATABASE Test1

TO DISK = 'C:\temp\20130319_1.bak',

DISK = 'C:\temp\20130319_2.bak',

DISK = 'C:\temp\20130319_3.bak',

DISK = 'C:\temp\20130319_4.bak',

DISK = 'C:\temp\20130319_5.bak'

The multiple backup devices should ideally be on separate devices, i doubt you'll see any improvements.