a little wiggle room, amp, 10'' boston g5

Considering purchasing one 10'' Boston G5 (450 rms) & possibly a Gtr most likely be in a sealed enclosure. Now i know to match the rms rating of the sub to an amp of roughly the same value. I also read in previous posts that boston underates their equipment which is good, meaning they will peform better than rated for. And can take a lot more power before blowing or even becoming distorted. How much more power?  Does anybody have any ideas. Also I have read small sealed enclosures are not as efficient as other types of enclosures (like a ported box) and take more power to make the sub louder and or more efficient. So does that mean I should give the sub some more power if I have some certain percent of wiggle room. Also as far as the amp goes having some extra power isn't bad either right ; (ex if I had a 200 rms sub I probably wouldn't buy a amp that is only capable of 200 rms cause it would be runnin at full steam all the time which probably I'm guessing not good) . So buying a 450 rms amp to match the sub I am figuring is not enough but what is enough with all this extra wiggle room.  

just want to know what type of amps I should be looking for. reason being is i went to a shop and he told me a good match would be a kenwood xr-1s or a jl hd7 both put out 700rms x1 @ 2 ohm. wanted to know is this overkill for a G5, or is a good match since the boston can supposedly handle more than it is rated for @ 450 rms. is he just telling me that to spend more money for these larger amps, where I could just find an amp that puts out 500 rms x 1 @ 2 ohm. I am willing to spend more money on a larger amp if indeed the sub can really handle it. I would like to here peoples thoughts about what they know about this sub

It wont hurt to get a bigger amp. I'm not sure what it can actually handle because i have never personally owned a Boston subwoofer. Even id your subwoofer cant handle the extra power you might wat to upgrade down the road, and having a more powerful amplifier will make that upgrade much easier. Have you ever look into the JBL amps? They might be a little cheaper then the ones suggested to you already. Check out the JBL GTO7001, It also puts out 700 RMS at 2 ohms and can be found for around 240 bucks.