RMS == root-mean-square...This is not the average power of and AC signal. RMS is roughly equal to the peak to peak AC voltage * 0.707. What this gives you is the appox. equivalent DC voltage. In other words if you were to apply 1.0VAC peak to peak current to a load it would be the same as applying 0.707VDC to that load. Your home is wired at around 120VAC-RMS which is 170V peak to peak AC. RMS AC voltage values are used because they give us a more accurate indication of the power that can be applied to the load.

What does this have to do with amplifiers and speakers? Simple. First please understand that car audio product specifications are almost always garbage. A lot of reading between the lines is necessary.

Any amplifier should be rated within the expected parameters of its operation. In the case of car audio amplifiers the parameters are:
1). The range of human hearing: 20hz – 20,000hz
2). The available power supply to the amp i.e. alternator: 12vdc-13.7vdc (13.7vdc is a stretch but most are rated at this max value.)
3). % THD-Total Harmonic Distortion: humans can perceive as little as 1% THD. (THD is the noise the amplifier adds to the original signal as it is amplified. As amplifiers reach their output or volume limits the THD goes WAY up!)
4). Expected load in ohms. (This load varies from around 8ohms to as little as 1 ohm. An ohm is a unit of electrical resistance and can be thought of as a restriction to the flow of electricity.)

To answer you question as to will it work depends largely on your music choices and desired volume levels. If you hook everything up correctly then yes it will work but maybe not as you would like. If you like very dynamic music at high volume (2-10” subs yeah I think so) this system may be a problem. Why? Amp quality not power.

RIOT RT850 Monoblock Amplifier
Max power, 2 ohm
850w x 1
RMS power, 4 ohm
200w x 1
RMS power, 2 ohm
N/A
Bridged power, 4 ohm
N/A
Signal-noise-ratio
>105dB
THD
.01%
Frequency Response
N/A
Size 8" W x 2 3/4"H x...
9 3/4"

This amp plays the “spec game” common to car audio. It is not what is stated but what is not stated that causes concern. At 2 ohms (your proposed load with two 4 ohm subs) the manufacturer does not tell you anything about the distortion dynamic, frequency range, headroom or damping of this product. My guess…this amp will be hot as hell(short life), have little dynamic power(speaker killing clipping) and sound like crap when cranked. There is a reason some mono blocks are <$100 and some are $1000+ w/ the same rated power!