Combine the results of two distinct Get-ChildItem calls into single variable to do the same processing on them

I'm trying to write a PowerShell script to build a list of files, from several directories. After all directories have been added to the main list, I'd like to do the same processing on all files.

This is what I have:

$items = New-Object Collections.Generic.List[IO.FileInfo]

$loc1 = @(Get-ChildItem -Path "\\server\C$\Program Files (x86)\Data1\" -Recurse)
$loc2 = @(Get-ChildItem -Path "\\server\C$\Web\DataStorage\" -Recurse)

$items.Add($loc1) # This line fails (the next also fails)
$items.Add($loc2)

# Processing code is here

which fails with this error:

Cannot convert argument "0", with value: "System.Object[]", for "Add" to type "System.IO.FileInfo": "Cannot convert the "System.Object[]" va lue of type "System.Object[]" to type "System.IO.FileInfo"."

I am mostly interested in what is the correct approach for this type of situation. I realize that my code is a very C way of doing it -- if there is a more PowerShell way to acomplish the same task, I'm all for it. The key, is that the number of $loc#'s may change over time, so adding and removing one or two should be easy in the resulting code.

-Filter is more performant than -Include, so if you don't have a lot of different extensions, simply concatenating two filtered lists might be faster.

<!-- language: lang-none -->

$files  = Get-ChildItem -Path "H:\stash\" -Filter *.rdlc -Recurse 
$files += Get-ChildItem -Path "H:\stash\" -Filter *.rdl  -Recurse 

I compared the output with a timer like this:

<!-- language: lang-none -->

$stopwatch = [System.Diagnostics.Stopwatch]::StartNew()
# Do Stuff Here
$stopwatch.Stop()
Write-Host "$([Math]::Round($stopwatch.Elapsed.TotalSeconds)) seconds ellapsed"