Actually, just to try to sort out the confusion.
There are (unfortunately!) two "SWM13" devices. The DSWM13 that Claude mentions is a multiswitch, designed for hotel installations where the cabling is "loop thru" rather than "hub and spoke" like residential cabling systems, and reduces the need for in-line amplification. The DSWM has a higher output than regular multiswitches, don't know how much higher though, no-one seems to have the specs, and that means it is capable of driving longer distances. You need to use taps to reduce the signal levels to the receivers, particularly those closest to the DSWM13, so would be useful in the OPs type of installation. But it's not available except for hotel installations.
The SWM13 (not the DSWM13) is not a multiswitch, it's a 13-channel SWM LNB that goes at the dish. But it has the same output level as the other residential LNBs and multiswitches, so does not help you if you are trying to drive longer distances, particularly with multidrop configs like the OPs. The SWM13 is only available at the moment in certain test markets, but even if it was available, it would not help the OPs situation. It would actually make things worse, because the device is at the dish so you would have to add the additional signal loss on the cable from the dish to the house, which using the SWM16 avoids.
So given that the "perfect" solution might be to use a DSWM13 with taps, but that not being available(and even if it were it would most likely be expensive), and since the OP already has an SWM16 and splitters, the obvious solution is to add the SWM amplifier. Not too close to the SWM16 (to avoid signals that are too "hot" for the first couple of receivers).
Note that since we don't know what the maximum recommended signal strength is for the receivers, putting the amp at the SWM16 might be OK. You could also put it there if you used taps instead of splitters for the first three or so receivers. But unless there's a big problem we don't know about, using the amp after the first two or three splitters looks like the best current solution.
It might be that at some point the DSWM13 switches begin to filter onto the market (eBay etc) in which case the OP could always use that plus taps to rearchitect the configuration. But it simply might not be worth it.
