Those Frugal Horns are highly efficient and gain a db or so mechanically for their back loaded horn design. You can drive them with a hand full of watts but extra headroom is always welcome. Never heard the Frugals but I still lust after the HS Horns which are a similar design. If you get the Frugals you could end up rolling amps instead of tubes.

Be forewarned, once you enter the realm of the full range driver you may never return.