soldering iron

Any soldering iron can go fine. It depends on your soldering skills. You can grab a great solder under $20 as others mentioned. Get some solder iron cleaner as @kosst_amojan mentioned. Get a soldering station as well. It works more professional.

If you need a reliable soldering iron, probably the best option for you is a mini soldering station https://toolboom.com/en/mini-soldering-station-goot-px-601/ like Goot PX-601 – it is almost the same size as a traditional soldering iron, but it has an option of temperature adjustment from 250 to 450°C. 80 W power should be enough for most applications. Great Japanese quality and it looks stylish :)

Things get much trickier when soldering to terminal posts.You need a high wattage pencil for this preferably 60 watts chiesel type,or a soldering station that can go up to 1200 degree F.If you were soldering at any other location the wattage and temp. is not as critiical.If you need to apply a resistor to a terminal you really have a big risk for a cold solder joint because a terminal requires so much heat to form the solder properly.You have so much more metal to properly heat up.It's just something I've learned from my years of soldering.You need alot of wattage and heat at this particular location IMO.
Good Luck and be Patient and Careful.

I use the adjustable Weller model # WLC100. Adjustable 5 watts to 40 watts.

If I may add to the fine suggestions already made.

I have two soldering stations, one being the Hakko 936 and the other a Tenma. They both work great & I use the Tenma more because I keep a smaller tip on it, as compared to a chisel tip on the Hakko, although the chisel is only twice the size of the point. The Hakko has the lighter wand & if you spend a lot of hrs. soldering, this may be a factor.

For lighter work I set the temp ~650 & for spkr. wire type work I run ~850.

Tinning the tip is of utmost importance & make sure the tip is tight to the wand if you use a non-fixed tip. Also, I've found using a wire type tip cleaner works better for me than a sponge.

Size of the tip is less important than the temp, as you can manipulate the wand if necessary.

If you need accurate temp. control, I'd suggest a digital readout or calibrated knob, otherwise a basic soldering station that still has an adjustable heat range will work fine, like
this one

reno a 40 watt iron is likely appropriate for that job

I recently posted this question on audiogon and was given the following excellent advice:the Hako 936.excellent machine

appreciate the responses, I spoke with the amps tech and he is sending out a resistor that I need to solder to some caps, he mentioned there are a bunch of wires attached to the terminal so what heat range would be appropriate, thanks again

I was in the same boat till two days ago when I bought a 40 watt Weller for $ 16.99 at
Sears Hardware, 7 year warranty.
Hakko is very good quality too.

Next up is this nice Mini Solder Pot from a company called Hexacon for about $ 70.00
Part # MP-945, 946, 947 or 948 depending on your temperature preference (last number denotates temp. in degrees) perfect for my wire stripping & tinning chores.

the main item of concern is the iron's power rating, which is determined by the type of work you want to do. If you are soldering / desoldering components on a circuit board, then use a 25 watt iron with a pencil point tip shape. If you are soldering wires, then a 40 watt power rating with a spade tip shape is more appropriate. If you are doing heavy work then a 60 watt iron is probably going to work better.

I usually use a Weller iron myself but there are many good choices available. I found a nice little dual-heat 25/40 watt iron (with a selector switch) that I like to carry in my field service kit (I think it was from RadioShack).

Adding to Jasljs's good post: The wattage has to be appropriate for the job. If there isn't enough, you will get a cold solder joint. Too much and applying to much heat (contacting for too long) and you start melting things other than solder. The lowest wattage irons are only good for component replacement, but won't nearly be enough heat for the speaker binding posts. For general purpose use, a spade tip, like a common screwdriver, is best. A pointy conical tip will drive you crazy with inadequate heat transfer most of the time, unless doing very fine work. And don't move until the solder solidifies. Blowing helps.

3 thangs to remimber when soldering ,one tin the tip frequently second keep the tip clean by wiping it with a clean wet sponage and third heat the component leads with the solding iron and apply the solder to the heated component leads as well, this prevents a cold solder joint in the future ,in regarts to buying a soldering iron unless you solder alot any $15 iron at say Radio shack type place will do just fine.