100db (at DC, AC gain is a little more complex to express), that's a gain of 10,000,000,000

I think you need to divide dB-volts by 20 first, so 100/20 = 5, which is the exponent,

or 10^5 = 100,000 is the open-loop gain.

Yes, 741s are first gen, and not so good. Better choices for inexpensive opAmps

are TL081, LF353, LF442, etc, all available from jameco.com. And not to mention

newer CMOS opAmps like LMC6442.

For high-gain "closed-loop" operation, eg X1000, the most important factor is

the Gain-Bandwidth Product value. I seem to recall 741 GBP = 1Mhz, which

means at X1000, the BW = 1Mhz/1000 = 1000 Hz, which is pretty low.

Some of the other amps mentioned have GBP 5-10X higher. For hi-gain situations,

it's common to use 2 opAmps in series with lower gain in each, then you can get

both hi-gain and also hi-BW.