A resistor question for CAT SL-1...help needed

A 1/4Watt would definitely suffice for input resistor for the cartridge.

The simple rule is that the total resitance if you connect a resistor R and 47k input resistance in parallel will be smaller than R. Since 47K is much larger than 100Ohm you may
a)replace 47K resistor with 100Ohms
b)Connect ~101Ohm resistor in-parallel with 47K Ohm resistor.

The general formula for your application goes from the following formula of the resistors connected in-parallel:

Rtotal = R1*R2/(R1+R2)

where Rtotal is the resistance you desire, R1 is 47K resistor and R2 is the actual resistor you need to match your experimented values

Rearranging the formula for R2 as follows:

R2 = [Rtotal(R1+R2)]/R1

Using these relationships you can build your own resistor bank that will step thorugh as many values as you desire until you find the best load resistance.

You may get a RadioShack project breadboard for such xperiment.

Marakanetz's advice is correct.
However, I want to add 1 important aspect: if you are using a MC step-up then make sure that you account for the impedance transformation owing to the xformer: whatever resistor value RCA plugs you make WILL get divided by the square of the turns of the xformer. So, if you are using a 14dB step-up, which is a 5:1 xformer then 100 Ohms effective resistor will be divided by 25. So, on the cartridge side the effective resistor WILL NOT look like 100 Ohms anymore!
So, in the step-up case, if you want the cartridge to see 100 Ohms, you should make 2500 Ohms RCA plugs (1:5 step-up case). Modify if you have any other value step-up.
The cartridge output is 0.4mV & so power developed across the phono load resistor is tiny. A 1/4W resistor is plenty.
Hope that this helps.

I agree, 1/4 watt is way more than enough, and don't worry about the tolerance. If you buy a resistor assortment at Radio Shack, any 2 of the same value will be from the same batch and will be very close to each other in value.

Thank you so much for all your comments, it really helped and my question was answered. Time well spent!!