If you are using 120Mb product (or, i practice, the 100Mb product) you will definitely need at Gigabit router.
Having quickly looked at the products you have linked to only the Belkin F5D8232 N1 definitely states that it has the three aerials that you do require to get the best out of Wireless N.
Ex <n>ildram , been to SKY MAX - 15,225 Download
BE Unlimited - 21,000 Download 1,200 Upload ON THE LINE THAT SKY COULD ONLY PROVIDE 15,255 DOWN AND 800 UP ON!!!,
Moved house, now BE Unlimited 6,500 Down, 1Mb/s up - gutted!
FTTC Cab installation commenced 12th April - expect full 80 / 20 - bye bye BE, hello BT Infinity soon!