Sand Beds - thoughts?

I'm picking up sand for the 75 on Monday.  Interested in thoughts on DSB, shallow bed, and plenums.  I have a shallow bed in my 46 (1.5") of course substrate.  I have had no issues with it and the tank has consistently been nitrate free.  In the 75 I want to go to a finer substrate to allow more options for sand dwelling critters.  My first thought is to stay with a shallower bed of the finer sand, and put a deep sand bed in the sump refugium.  The sand I am getting would allow a 4" bed in the fuge and a 2.5-3" bed in the tank.  Seems like the more I read the less there seems to be a consensus about DSB's.  Advanced Aquarist did a controlled experiment and found zero impact to the tank's ability to process wastes based on depth of sand and the presence or absence of a plenum.  A plenum seems like a good idea, but it must be old school, doesn't seem like many people are running them.  Thoughts?

The most common thing to do nowadays is a couple of inches or less and pretty much what you have in your existing tank.  Finer sand can limit the flow capabilities in your tank.  

DSBs can be problematic over time.  I still like the idea of them but feel it would be best to run one so it can be easily removed from the sytem if needed.  I haven't ever had one so this is just from the reading I have done.  I am considering one for my fuge in my second tank.  I can tell you that when I heard Scott Fellman speak last Winter, he still considered them a good option.  He was speaking on husbandry too so I think if done right, they can have some merit.

I can't speak of plenums at all.  They are, as you say, old school.  One thing though, I still hear of people having DSBs but not plenums.  ?  

Hopefully, someone who has actually tried a DSB and or plenum will chime in.

I'm curious, what sand critter do you hope to keep?  It seems many of them are just as happy in 2 inches as they are in more.

The critter consideration is for the type of sand, not the depth. I haven't made any decisions yet, but want to have options for sand burrowing species of fish and inverts that I don't have with my current very coarse substrate. I also want a different look for the second tank. I am leaning heavily towards a shallow bed of finer sand for the DT. Not sure what to do for the fuge, the same I suppose? Although it would be easier to add and control sand sifters to the fuge as opposed to the DT. I understand with a DSB it is important to keep it turning over. I am picking up sand tomorrow, I will have extra if anyone needs any.

I have a fairly DSB about 4 inches. I have not had a problem with Nitrates etc, except if I miss a water change. I like it as those burrowing critters, pistol shrimp go deeper if they have the chance. I have fine live sand. It doesn't get high up in the water column if someone stirs it up. My damsel and the lone tomato clown like to swish up divots in the sand and it just settles back in. I will agree with others, that is you have to suck up dirt etc. on the sand you have some to spare. I like it for rockwork too. I have been foaming in the bottoms, to prevent scraping and tipping over.
The deeper sand covers that. So I guess I am a medium DSB.

Some brave soul just posted about cleaning out his DSB in a SPS tank on Reef Central. He posted vids too. Search for a thread with DSB and SPS if you want to see what I'm talking about.

Found it.  http://www.reefcentral.com/forums/showthread.php?t=2361052&highlight=dsb+sps

I clean out about five 5 gal buckets every week that look as bad if not worse out of the 210 at the science center, but oh my for little creatures swimming just above the sand!

I ended up putting in 2" and calling it good. Looked like if there was any advantage to a DSB it came with a higher maintenance routine than I am willing to do. Same for the fuge. Especially after reading the Advanced Aquaria tests which showed no benefit, at least short term.

Yep used DSB's for years they work great but if you want quicker bio filtration mechanical and LR.is your best path.