NHT 3.3s are very position specific ... according to the manual you must place the back of the speaker 3 inches from the back wall so the speaker and the wall create a corner ... the corner gives you a 3db boost in the bass region and this has been compensated for and built into the crossover
If you pull the 3.3s out into the room as you would a normal speaker ... they lose the boost or gain in the bass region created by the speaker/wall creating a corner and can sound lean or thin
Unless they are set up this way ... they will definitely sound bass shy and tipped up or a bit bright in the treble ... eliminating the jumpers or bi amp-ing them is totally unnecessary but they do need some watts due to their some what lower 87 to 89db efficiency ... 150 watts of good clean power is all you would need to make them sing
Your listening position should be 1.25 to 1.5 times the distance between the speakers ... my 3.3s are 7 feet apart and I sit 9 feet off the front baffles ... at 50 to 75 watts on my amp's meters I get 92db at my seating position with peaks around 97db ... if I turn the amp up a bit so it pumps out 100 watts or so on it's meter ... 102db on the peaks are easily produced at my listening positon 9 feet off the speakers front baffles .. no problem
With 102db peaks they don't sound loud ... strained or in your face but very authoritative with real life size scale ... narrow front baffles has them image and disappear like the best mini monitors
The 1259 NHT part number for the woofer is also used in their 12 inch stand alone subwoofer and some other subwoofers of that era .. so you shouldn't have a bass issue ... you just don't have them set up correctly or are not feeding them enough watts
This is all clearly detailed in the owners manual about distance to the wall and spread to seating distance measurements ... I'm sure I have my owners manual somewhere ... if you can get me your mailing address I'll send you a copy
Just get a piece of wood exactly 3 inches wide and place it against back wall and push the speaker up against the wood ... now you're 3 inches from the back wallEnter your text ...