I use a twin 20 for one system, a twin 30 in another room, and a single 40 without sides as a piece of furniture on the other side of the house.
I cut the aluminum risers on my twin 30 with a chop saw and carbide tipped blade. then drilled and tapped the riser. Simple clean neat, and now a custom height. A Toshiba widescreen direct view (185 lbs) now sits on the top, and a center channel benath (no center post in the front), center channel beneath the TV.
I have found that the optional casters are high quality, look good and work well. My other racks have the optional polished legs, which look great. Either is HUGE step ahead of the standard feet, which work great, but are very ugly in comparison.
The racks require some patience and thought to assemble without scratching anything. But it is not difficult by any stretch. Just remember to thread things into the posts, while holding the post stationary. If you rotate the post instead of the bolt, you will scratch the shelf. The veneer looks good.
The perforated side panels are a must. The keep a lot of dust out and look good. I don't have any doors or drawers, so i can't speak to those. I've never even bothered trying to install the back panels on any of my Synergy's. They seem completely unnecessary.
Once assembled, the rack is rigid and stable. The shelves require a knack to adjust and level, but with the supplied level, and a one side at a time approach, is very straight forward. Having adjustable shelves is a real plus as your system changes over time.
I also own a Zoethecus rack, similiar to a single 50. The Zoe is far more attractive, rigid and stable. But it is a fixed shelf rack, and costs twice as much (if not more with the z-slabs).
I can't say enough about the Salamander Synergy racks at their price point (and for a lot more $$). On the high end Zoethecus and Billy Bags are difficult to beat. But cost and fixed shelves are a downside.
I have no experience with the Archtype, but they always struct me as "wobbly".