I feel like I'm a member of a small but enthusiastic club. I own a pair of SAM's, a pair of updated Super 3's, and Louis is working on a pair of 1.5 RS5's. I also own a pair of Rythmik F8 active bass modules. I can use any of these mains with the bass modules.
It looks like you have a pair of RS5 1.5's in what is similar to a SAM cabinet. My SAM's sit perfectly on the F8 modules supported by Herbie's Square Fat Dots. As an alternative, I can quickly sub in a pair of 1.5 monitors for the SAM's, adding an Isoacoustics stand (4.75") to correct for height.
The 1.5 way RS5 and the Alnico Monitor are interesting companions. They both are able to move a similar amount of air and in my opinion are of similar midband efficiency. While my dedicated listening room (the smaller of my two spaces) is in a state of reconfiguration (based largely on the invaluable insights of AC members and vendors), my living room/HT room is coming together nicely in time for winter. When I get the 1.5 's in I will share some comparisons of all three configurations.
I will offer two additional thoughts: it is liberating to remove the need to produce deep bass from a high-efficiency speaker; once we stop trying to reproduce 30hz from a 4" or 6.5" driver we can focus on what they do well, not force them to do something they don't want to do. I've also come to appreciate that much of what we value as "bass" is in reality mid and upper bass. By choosing stereo bass modules we can run them higher and fill in (or boost, if we prefer a House Curve) the falling midbass of many full-range drivers.
I will also offer my appreciation of AC vendors, specifically Omega, GR Research, Rythmik, and GIK. In order:
Omega: IMO offers the best variety and value in high-efficiency speakers on the market at the moment. They are all essentially made to order, and within the context of Louis' design philosophy can be customized to whatever the customer wants. However, Louis only offers one bass module at the moment, which is great for a smaller space or for models with solid midbass performance but may not scale to all applications.
GR Research: Danny is one of the good ones. I own some of his kit speakers (XLS Encore and XCS Center) and when compared to similar speakers of conventional efficiency his are killer values and great performers. He is one of they guys working on open baffle applications at a fairly high level (with high efficiency as well). I highly recommend the T26SG tweeter (94dB) he offers for $50 as the ideal supplementary tweeter for Omega speakers where one is desired, preferably firing upward behind the speaker crossed over at 15 kHz or so.
Rythmik: IMO these are the guys to choose for bass applications. If we choose paper-coned models (F8, F12G, L12) these servo-controlled bass modules are "fast" enough to keep up with the RS5 while producing tremendous bass. I run my F8's as high as 200hz. I bought stock models second hand but they are also available for custom installation. Louis has been very accomodating in putting these products into his excellent enclosures. IMO, these factory-direct bass modules compete head to head with products from Rel, L Audio and other manufacturers.
GIK: These guys are terrific. Not only are their products attractive, inventive and affordably priced, they offer free design services to help you set up your room. The value is of the charts.
I will also throw out my appreciation for AC members who have provided great inspiration. This is a great community who are a wonderful resource.