from Harbeth 30.1 to SHL5+, an upgrade or lateral move?

To Rossb: The type of music I listen to is classical , jazz, vocal, pop. I agree with you that 30.1 has a very refined and natural  midrange. However, I feel the urge to upgrade because the soundstage of 30.1 is not wide (it could be due to my small room: 12 x 15 feet) and contrabass in jazz sounds weak and thin, which makes the song does not have the necessary bass. 

Do you experience the same on your 30.1 pair? I am using Quad 99 and 909 for it. 

@quanghuy147
In that size room you should give a listen to the smaller P3ESR. Bigger is not always better. I've owned larger Harbeths and preferred the P3's in my smaller room!

@quanghuy147 It looks like you gotten some solid advice.  Per some earlier suggestions, why don't you try using a subwoofer first.  If you have audio stores that will allow you to audition at home, great.  If not, go to BestBuy or Crutchfield and try out one of their subs.  If you think it improve the sound and gets you closer to what you're looking for, keep it or consider buying a higher end like a REL or JL subwoofer. Many Harbeth owners use REL in their setup, just like @donjr.  It's a great combo.  I usually don't like the idea of buying something to return, but without any real brick and mortar shops to audition equipment, not much of a selection or not much of a choice.    

I know all the discussions here are centered around comparing the speaker models but if you really like the sound of your current speakers and just need more bass, you may want to try a different amplifier - or even a preamplifier, to see if they can plug that missing bottom end. I don't know the what the output impedance of the Quad amplifier looks over the frequency range but if they were designed to match/support the weird impedance curve of the Quad speakers, it may simply not be a good match for the Harbeth speakers. Just something to consider.

"Do you experience the same on your 30.1 pair? I am using Quad 99 and 909 for it. "

I mainly listen to classical and jazz. I find the soundstage perfectly fine, but then soundstage is not something that concerns me too much.

I also find the bass to be satisfactory. Obviously, the 30.1s do not go very deep, and a bigger speaker or subwoofer would go much lower. But I don't find the bass with the 30.1s "weak" or "thin".

As others have suggested, it could be an amplifier issue. I'm not familiar with your Quad amps, and I'm using Exposure (MCX preamp and 3010s2 power amp). It might be worth trying another ampllifier to see if this improves things.