go with combination 1 that way your giving the sub a little more power and in case you ever want to either get another sub or upgrade to a better sub you have a strong amp and you wont need to buy another one
if you want to conserve money and are sure that you wont change your setup then you can go with combination 3...but whatever you do dont go with combo #2 those Type Rs are built good but not to take 1000rms
The only problem I see going with the MRD-M605 amp is that it is only 1000w max. The alpine Type R subs are 1500w max. I won't really be getting the full effect if I get this amp right? I'm thinking of going with combo #1 if that is the case