Equipment does not match

i am still learning about this stuff, so the specs of the equipment might help;
B25s Description: Three-way, reflex-loaded, floorstanding loudspeaker. Drive-units: 30mmx40mm Air Motion Transformer tweeter, 5.25" (130mm) Kevlar-cone midrange unit, 9.1" by 6.5" (232mm by 165mm) air-dried paper-cone woofer. Crossover frequencies: 180Hz (third-order Butterworth), 2.7kHz (second-order). Frequency response: 35Hz–45kHz, ±3dB. Nominal impedance: 4 ohms. Sensitivity: 88dB/2.83V/m. Recommended amplification: 200W. Maximum SPL output per pair: not given.

Pre amp SP17 / 17L Specifications:
FREQUENCY RESPONSE:
Line: +0-1dB, 0.6Hz to 80kHz at rated output. -3dB points below 0.3Hz and above 120KHz.
Phono: +/-0.3dB of RIAA, 10 Hz to 20KHz
DISTORTION: Less than .005% at 2V RMS output.
GAIN: Main output line: 11.1dB Processor: 0dB.
Phono: 58dB at 1 KHz.
Record output, line: 0dB. Phono: 47dB.
INPUT IMPEDANCE: 60K ohms line, 47K ohms Phono, (0.7 to 7mV High output cartridge recommended). Inputs (6): phono, CD, tuner, video, aux, processor. Model SP17L has no phono input.
OUTPUT IMPEDANCE: 210 ohms Single Ended main; 20K ohms minimum load and 1000 pF maximum capacitance. Outputs (3): 2 main, 1 record (Single Ended RCA connectors). Record output 60K ohms minimum load and 100pf maximum capacitance.
OUTPUT POLARITY: Non inverting.
MAXIMUM INPUT
Line: 9V RMS.
Phono: 40mV RMS 1KHz, 100mV RMS 10KHz.
RATED OUTPUTS: 2V RMS into 100K load. (Maximum output 15V RMS at 1% THD at 1kHz.)
POWER SUPPLIES: Electronically regulated low and high voltage supplies. Automatic 25 sec. warm-up/brown-out mute. Line regulation better than .01%.
NOISE:
Line: 12uV RMS IHF weighted at main output with volume low (104dB below 2V RMS output).
Phono: 0.3uV RMS IHF weighted equivalent input noise, shorted input (76dB below 2mVRMS 1KHz input).
TUBE COMPLEMENT: (2)-6H30 dual triodes.
POWER REQUIREMENTS:100-135VAC 60Hz (200-270VAC 50/60Hz) 39 watts.
Power amp
The RB-1080 rests close to the pinnacle of Rotel's two channel power amplifier designs. Power output of 200 watts per channel (20 Hz to 20 kHz @ 0.03% THD into 8 ohms) is extraordinary. The Rotel-made toroidal transformer feeds separate power supplies for each channel, each with its own rectifiers, voltage regulators, and capacitor banks. Damping factor, at 1,000, shows this amplifier's unparalleled ability to lock onto the most difficult speakers to precisely control diaphragm motion and give you the best sound quality. Switchable balanced (XLR) and unbalanced (RCA) inputs provide flexible system interface. Front panel heat sinks add a strikingly dramatic look and serve a functional purpose by enhancing heat dissipation even in cramped environments. And a separate input and output for 12 volt "trigger" signals makes this amplifier well suited for fully integrated systems with total remote control capability.

likly, your cables!, cables play a profound part of every systems sound.

Dereck -

a much better power amp match w/ your ARC pre, would be, Bryston 3B ST /SST or 4B ST/SST.

Only one response about the room,interesting.
I went the upgrade route with gear and (god forbid cables)spent 10's of thousands on the above.
The most immediate and huge improvement was using acoustic panels(especially bass trapping)which give you a tight punchy bottom end and also freeing up the mids and highs,a non muddied clean sound.
Speaker position,seating position and if that doesn't do it,the room,heck you can go to a hardware store and put unopened bags of insulation in your corners to hear what happens and its free as you can take them back as they are unopened.
Haven't heard a cable yet that even touches what acoustic panels will do for sound.
Even put a radio or boom box and play a track in the bathroom and then put it in your room and you'll hear a HUGE difference or even run your speakers to a different room and the sound WILL CHANGE.

Have you tried placing a rug in front of teh speakers at the
main reflection point to where you liten from? Bare marble
floors sound like something that might benefit from a bit of
acoustic treatment. If bare walls also, an acoustic panel
on each side wall at main reflection point to your listening
position might be worth a try.

Also before that, sound like speakers might be too close to
the walls for best results.

The Sereophile reviewers positioned them 5' from the front
wall:

"I positioned the Burmester B25s 5' from the front wall, 6'
apart (measured from the tweeter centers), and toed-in 45°
to focus on my listening chair 7' away."

I'd play with the placement aways from walls a bit for good
soundstage and imaging and then perhaps try floor and/or
wall treatments from there as needed. Maybe try the toe in
as well. definitely get speaker placement optimized
before anything else.