-> Tower Inn:

I've stayed two times at Tower Inn Silom, and both times I got a room on the "Executive Floor" - both cases large rooms, but really a bit run-down (Tarntawan: not really run-down, in my opinion); I had the impression, they rent the "run-down" rooms for this internet rate of about 1500 bt. (these rooms look worse than the rooms in the internet sites of tower inn).

-> Pinnacle:

You book your room with Jimmy - you can see him as a travel agent. When you check-in in Pinnacle Hotel, they normally do know that you've booked the room via Jimmy, and you don't pay them directly (only for the minibar and roomservice etc., of course - that's why they ask for a credit card at check-in, of course). You pay Jimmy (usually pre-payment - meaning, you check in, get your room, than you go to Jimmy and pay him for the room).

Pinnacle is a bit far for walking to Silom Road, I think (especially with the high tropical temperatures of Bangkok), better take a taxi-meter.