Mac Pro :: Wireless Connection Is Very Slow , Every Web Page Open It Take Minutes To Open?

i've just bought my new mac pro, i'm very happy with it's performance, but there is 1 small little tiny problem, i've ordered my mac pro with wireless card, but my wireless connection is very slow , every web page i open it take minutes to open, before i had an imac, the wireless connenction was super fast, then i've sold it to my dad , but my new mac pro is very slow, mention that it's in the same room and in the same place my imac was.

i've check my bluetooth, i've send and receive some files with my bluetooth to my moblie, it was great, but when i copy files from my brothers computer it was slow and then it stucks , with my imac this never happens.i opened my mac pro to check the wireless card and i found this:-
antenna 1 was in the bluetooth card.
antenna 2 was in the upper wireless card.
antenna 3 was in the lower wireless card.

the weird thing i've found is that my speed connection it goes fast and then is goes slow then fast then slow, it's not stable, another weird thing is that my wireless speed is slow then when i press the wireless bars it goes fast then it returns slow again.this is a really lousy service from apple to make the wireless card as optional , it's really unfair i mean it is the most powerfull mac ever and wireless is not included one more question, is there a difference between the wireless card in the imac and in the mac pro?