I'm just guessing, based on your previous post. But let's call the drivetrain the crankset, the rear cassette, the derailleurs, and the shifters.

Before we proceed with the drivetrain, let's get one other issue into the mix: Your handlebar. It's too low for your comfort, and you have issues with being low in the drops. A drop bar should be more or less at the same height as the saddle. If your drop bar is positioned correctly, and you are uncomfortable with it at that height, you have two options. First, you can change to a hybrid-type stem. This will get your drop bars up higher. Second, you can change to flat bars, like on a mountain bike, which will give you more of an upright riding position, especially in combination with a hybrid stem. What solution you pursue will depend on how your bike is set up now, and what set-up you want to achieve. For relaxed riding, an upright position will be fine. For racing or long distance riding, you will want drop bars.

OK, now let's go to the drivetrain.

Let's start with the shifters. From your post, it sounds like you have two issues with the current set-up. One issue is that the shifters are friction-- is that right? The alternative, if you don't want friction shifters, would be indexed shifting, meaning you have a precise shift to a specified gear when you shift. In contrast, friction shifting depends upon "feel" to reach the right gear. The trade-off is indexed shifting is more sensitive to slight misadjustments. The second issue is where the shifters are located. It sounds like you don't like to reach for downtube shifters when you shift. You have a few choices here. One choice would be brifters, with the shifter and brake lever combined in one unit. This set-up would allow you to ride your hoods and shift without reaching for anything further away than your brake lever. Brifters would be indexed. You would need drop bars for this set-up. Another choice would be bar end shifters. These fit into the ends of your drop bars. They can be either indexed or friction. A third choice would be grip shift. These shift by twisting your handgrip like you would apply the throttle (gas) on a motorcycle. Gripshifters would be indexed, and would require a flat bar. A fourth option would be mountain type thumb-shifters, for use on a flat bar. These would be indexed.

Now let's go to the derailleurs. Your choice is indexed or non-indexed, although every modern derailleur would be indexed. Furthermore, because of indexing, every component in a drivetrain is designed to work with a "system." In other words, if you buy Shimano derailleurs, you would also buy Shimano shifters, a Shimano cassette, and a Shimano chain. The days of mix and match belong to the past. You will also have to consider whether you're running a double or a triple crankset, and the gear range on your rear cassette. The derailleurs must be rated to handle the gear ranges you're asking them to handle. thus, for a triple crankset, you'd want a derailleur that is designed to shift a triple crankset. For a wide-range cassette (typical on touring bikes, and good for uphill slogs), you'd want a wide-range rear derailleur. For a racing cassette, you don't need a wide-range rear derailleur.

For your crankset, you already know you want a triple. You still have to do three things. First, you have to make sure that you have a bottom bracket that matches your triple crankset. Second, you have to decide what chainrings (how many teeth) you want. This will depend on what gearing you're trying to achieve. Frank Berto's book can help you figure that out. Third, if possible, you will want a crank arm in the 150-165 mm range. Really, 150-155 mm will suit you better. You can get them here. Your choice of crank arm length *may* dictate your chainring selection.

Finally, you will have to choose a rear cassette and chain. Your choice will be dictated by your above choices-- e.g., Shimano indexed-- as well as by the gear combination you want to achieve in conjunction with your crankset. For purposes of simplification, if you want very low gears for getting up hills, you will want a wide-range cassette and a triple crank with a very low third chainring. If you want to race, you will want a rear cassette with narrow range gears and a triple with narrow range chainrings.

It sounds complicated, but it's not. It's just a question of understanding what you want, and what combination of components achieves that. Especially with modern systems, the entire drivetrain functions as a system, so if you decide on Shimano shifters, you would also buy Shimano derailleurs, a Shimano cassette and chain, and a Shimano-compatible crankset.

Does that make sense?