help on center speaker

Ok, let me make sure I understand this correctly: if you setup the speakers to full range (large speaker in the NAD's setup), the low frequency will not be cut for those speakers - for example my Linn Index's low range I believe is from 60 Hz. The rest of my speakers have a low freq range of 80 Hz.
In this case do I want to set the sub crossover to 60 Hz and front speakers to LARGE or I still have to set the sub to 80 Hz with front speakers to LARGE?
My intuition tells me that the second setting is the correct one.
Thanks a lot for the help!

If you can, use the same speaker that you use for your mains for the center channel. Actually use the same full range speakers all around.With large speakers this may mean building a new baffle to rearrange the drivers. It may mean building a different shaped cabinet to house the drivers, just keep the volume the same. Build a special cabinet to hold it over the TV, or put it behind a perforated screen. Be creative and come up with a way to use the same speaker. You will be glad that you did. The center speaker is very important, I wasn't satisfied untill I matched mine up.

Full range speakers arn't a waste. They allow you to set the crossover frequency to the sub much lower the 80Hz. Mine are set between 35 and 40Hz.

no, I would set the NAD crossover at 80hz (all channels) and all speakers small. Turn you sub crossover all the way up or disable it. Remember LFE is 120Hz and lower, if your subs crossover is in the way you will be missing information. A large speaker never sends anything to the sub, only small below the crossover setting...

I will keep it at 80 hz and small speaker setting, until I upgrade my front speakers.

Remember that the Afekt is factory set to match the Unik. If you put it with a "larger" speaker with better bass response than the Unik, such as an Index, you may find the bass a bit tubby. This is what happened when I put an Afekt with Tukans. I had to adust the Afekt so that it crossed over at a point more appropriate for the Tukans (i.e. lower). However, if you do this, it will now not match the Uniks, which you also have. You might not notice it in HT, but if you listen to newer formats of multichannel music, such as SACD or DVD-A, it may not be a good thing . This is one reason why speakers all around should be relatively similar, and full range, as opposed to the days when rear speakers only produced effects.

Regarding one of your other comments about front speakers having to be be full range, they don't "have" to be. However, if you have full-range speakers, you will have bass in stereo. This gives good musical reproduction. And for HT, let the sub take care of the non-musical booms and crashes. If you have small monitors, crossed over at a high point, with bass filtered out and handled only by the sub, you will have mono bass. Fine for HT, but there's a lot of musical bass in the 40-80Hz mid-bass region. (The open E string on a electiric guitar is around 36-38Hz) It won't be in stereo if you filter it out. That's one reason why some people suggest that you need two subs, ... or full-range speakers in front.

Some NADS have a reputation for audible hum and hiss. You have to live with it. NAD is good value for the money but you get what you pay for.

I think a Centrik would be fine as a centre It's more likely to match than a different brand, if you can find one. As far as other brands go, trust your ears. Remember Linn's philosophy: "if it sounds better, it is".