Just starting out

Passive preamps don't have a gain stage. The only voltage driving the amp will come from the cd player or dac above the preamp. Make sure the input voltage sensitivity of the amp is less than or equal to the output voltage of the cdp or dac or else the amp won't play at full power. Impedance matching is equally important.

Devilboy-
Would this apply to an integrated amp?
Plan was to go Media server->DAC->Integrated amp

Unless the integrated has a passive preamp section, incoming voltage, 2V,3V, etc, shouldn't be a factor since the preamp section usually would be active. You should note, however, the input impedance of the integrated. Incoming and outgoing impedance is important for EVERY component, regardless if it's cdp to preamp, dac to preamp, or preamp to amp. The general rule of thumb is that the output impedance of a component should be ten times LESS than the input impedance of the component it's going into. For example: if the output impedance of a cd player or dac (whichever your system has), is 5,000 ohms, the input impedance of the integrated amp should be 50,000 ohms or greater. 5,000 ohms is very high but they do exist. The industry standard for an amp's input impedance is 47,000 ohms.

Hi Devilboy-

I looked up the specs of the 700i and the DAC that I am interested in.

Integrated Amp Sim audio 700i 23,700 ohms Input impedance

Specs on Tube DAC-II-MK2 Accustic Arts are below
Digital inputs up to 192 kHz: 2 x S/P-DIF; unbalanced – 75 Ω (COAX)
1 x TOSLINK; optical
Digital input up to 96 kHz: 1 x USB 2.0
Digital inputs up to 48 kHz: 1 x AES/EBU; balanced – 110 Ω (XLR)
1 x S/P-DIF; unbalanced – 75 Ω (COAX)
1 x S/P-DIF; unbalanced – 75 Ω (BNC)
Digital outputs: 1 x S/P-DIF; unbalanced – 75 Ω (COAX)
1 x AES/EBU; balanced – 110 Ω (XLR)
Analog outputs: 1 x balanced – 2 x 33 Ω (XLR)
1 x unbalanced – 33 Ω (COAX)

Using your rule of thumb I should be OK. Correct?

Well, first of all, the input impedance of the sim is a VERY low 23,700 ohms. Personally, I wouldn't buy it based on just that spec alone. Even if your dac has a low output impedance, it kind of paints you into a corner acoustically. Meaning, if you keep the sim, you limit your dac choices to ones the MUST have a low output impedance. Apperently the dac you mention has a low output impedance of 33 ohms either from balanced or single ended, which would be ok with the sim. I think there are better amps (ss or tube), that would have a higher input impedance. Also, I don't see a mention of the output voltage of the dac. What is the input voltage sensitivity of the sim integrated?