Missing tube integrated for Klipsch Forte III?


2 weeks ago i acquired and set up the forte iii's in my 25x35 basement (8ft ceilings).  i paired it with a gorgeous yamaha as-2100 - man that amp is beautiful and solidly built.    granted, both the forte's and that amp aren't really broken in yet BUT (i hate) i am missing that low end bass presence that i hear so much about from tube people.   they all talk about "bass slam."   it's not that the yamaha doesnt deliver, but i'm just not feeling it as a slam.   i understand the primaluna evo 300 uses EL34 tubes and are supposed to be highly musical, dynamic, and able to slam.   reading all those reviews leaves me tempted to try to tube route.   thoughts?   looking for real low end at low volumes with great detailed resolution up top (but not too bright).   i do love the build quality and aesthetics of the yamaha - would be hard to see that go on a trade.   
mjb87062017
great comments, thanks to all.  i'd appreciate recommendations for a sub that pairs well with the fortes.   primary is 2channel music with some limited HT.   thanks 
Back in the late 80's I had Forte's.  I was new the hobby and didn't have the knowledge to dial them in and sold them quickly.  Years later I used a Jolida JD-1000a integrated amp in a 2nd system with Spica TC-50's and felt the Jolida would have been an outstanding match with the Forte's.  The JD-1000a of later models may be worth a little research.
How much bass do you want?  What size room?  How much space do you have?  Have you done any room treatments?  I'd suggest searching some of the existing threads on subwoofer usage.
audition_audio 
As you wrote, the el34 is a Pentode tube. The 6550 and KT88 ( also the  KT 90) aren't true triode tubes but are classified as power beam tetode/pentode. It is true that all of these types of tubes can be 'wired' to triode function. Many amplifiers offer a switch for choosing Ultralinear or triode operation. 
True triode power tubes are for example, 45, 2A3, 300b,PX25, 845, 211 etc.
Charles 
58hz is where the Heresy IIIs drop out, although "lower mid bass" until that point is amazingly good. I have a couple of Stereophile test CDs that show these facts to be true...and 2 REL subs adjusted to around 58hz to take the baton, so to speak.