Energy storage in IC2 is most efficient at the highest tier -- MFSU.
Greg tech energy storage is generally expensive for what it does.
For the 100 EU/t reactor i personally like to stick an MFE right on it. Use the redstone option in the MFE to control when the reactor runs. I haven't looked into how it handles overflow, so I just use emit when empty.
By overflow i mean how a plain generator wastes a ton of energy when it generates more than is being consumed -- a little trickle triggers a new coal or whatever to burn. I imagine a reactor supplying an MFE that is set to run it until the MFE is full would supply an extra 100 EU packet to top it off every time a little is drained (128 is drained, 200 is sent in from reactor). This option in the storage unit i believe is emit when there is space for power -- again not sure how it handle trickle usage, could be wasteful.
You could do one MFSU and attach 100 EU/t reactors to each side and do the same as above.[DOUBLEPOST=1363391218][/DOUBLEPOST]
If I can remember correctly, the max EU/t a reactor can reach is 2048EU/t. So I'd say just pop a HV-Transformer onto it and then glass fibre cable leading to whatever. If you have none of that, then either use HV cable or also place an MV-transformer and use gold cable. Though I highly recommend glass fibre cable due to it's very low EU loss rate per block.
EDIT: In case you don't know
HV Cable (fully insulated) - 1 EU lost every 1.25 blocks. Max intake is 2048EU/p (EV.)
Gold Cable (fully insulated) - 1 EU lost every 2.5 blocks. Max intake is 128EU/p (MV.)
Glass Fibre Cable - 1 EU lost every 40 blocks. Max intake is 512EU/p (HV.)
While reactors can run very high EU/t. You can use a cable/storage unit/transformer sized for the output of the reactor you have made. I have used tin cable on a breeder reactor (5EU/t) for example. And gold early game on any reactors under 128 EU/t.