Look at your current and future current (Amps) needs, then choose one that will cover that and more. If powering HF equipment avoid brands with known RFI issues.
In my opinion, Astron is one of the best power supply companies and I like their lightweight switching series like the SS-25M and SS30M. These are very reliable and if they break outside the warranty period Astron will fix them for almost free. I've made mistakes and blown up an Astron linear supply to bits and they completely rebuilt it for $20. This was a very old power supply that I bought used and they still fixed it and brought it up to the latest version and specs.
Astron and Samlex are the power supplies you usually see intended for radio communications applications. I think the Alinco power supplies are probably OK, too. If you find a deal on a used Icom, Kenwood, or Yaesu power supply, they would be OK, but they are too expensive new.
As for planning for future needs, don't simply add up the transmit current requirements of all your intended radios and think that's how much power supply you need. You aren't likely to transmit with more than one radio at a time, so use the highest transmit current of your selected radio and then add a couple of amps for each of the other radios to cover their receive current requirement.
Some people buy a power supply, connect it to the 6 devices, & throw it behind a table to live on the floor for 12 years out of site for that whole time. If this is you, get an Astron 35 amp HEAVY linear supply. If however you need to move your power supply often, then get one of the light switchers. Astron SS30 is great. I also own 2 MFJ 4230’s, & they are great. Not made by MFJ, they are also sold under the Jetstream, & QJE brand names. It’s better to buy one bigger than you need, than to buy what you need, & a year later it’s not big enough.
Most of the computer/server/router power supplies create lots of RFI on HF. You can get a 3,000 watt power supply in a box about 13 X 4.5 X 1.25" but you will need a box twice the size to hold all the filters needed to clean it up.
The Icom 7300 is a great radio and draws about 12 to 15 Amps average on SSB during transmit and about 18 to 20A in FM mode. An Astron SS30M with volt and current meters would easily handle the 7300 and a 50W 2m rig transmitting at the same time, which is unlikely but at least you know it would handle it.
I've bought two of the TekPower TP50SW 50 Amp 13.8V Analog DC Power Supply with Cigarette Plug units from Amazon.
I use one with my 7300 and the other with my 7100. I've found both examples I have to be quiet as far as the fan goes, and also as far as RFI is concerned. They have an adjustment knob that will move any RFI a little up or down in frequency, so on the rare occasion I am trying to hear a weak signal that seems to be getting some interference, I can move the knob to see if it's coming from my power supply, and if so, eliminate it by moving it.
Its a well documented problem with various fixes, mostly using ferrite. Do a Google search on computer power supply RFI and you will have lots to read.
The big high power server supplies are meant to plug into a mating chassis that has enough filtering to pass FCC specs. When we buy and use the individual power supply modules without the host chassis there is little to no RFI filtering in some of them. I use a number of multi kilowatt server supplies and have to install commercial Corcom AC input filters and hand make high current filters for the DC outputs.
As a youth, just starting out with a CB, a car battery was what I used. Since I was running "barefoot", it ran fine and I'd check the voltage every few days and put the battery on a charger when it got a little low. That worked fine for quite some time and I didn't have to worry about filtering.
There's a fair amount of leeway for a power supply that serves a 40w-50w 2M/70cm mobile radio. A 12-15A, 12VDC nominal should work fine. If you intend to get in to HF, a well filtered power supply is a must. Trying to operate with a noisy power supply is an exercise in frustration.
Lastly, running multiple radios simultaneously on a single power supply is fine. Keep in mind that radios will draw the most current during transmitting and You'll likely only do that on one radio at a time. I routinely run two - three radios at once on one 50A power supply and never have any trouble.
lots of good input.
I definitely want to buy the right one the first time.
I'm not trying to buy the cheapest. Probably don't need the best either.
But I want one what I wont regret buying. No need in being frustrated with what I buy.
And a couple people mentioned having one that is well FILTERED. One person recommended an ASTRON. How is the filtering on the Astron?
Or what are the good FILTERED power supplies on the market?