Yup, which Infinity's ??
So, if they are any of the models with dual voice coil woofers (?), you need an amp that is stable into a nominal 4 ohm load. That's pretty low impedance and not easy to drive.
The reason your current receiver cuts out is it can't handle the additive load. I'd really look at a used 5.1 or 7.1 receiver that can handle 4 ohm. These modern receivers have individual amplifier sections for each speaker group (front, rear, etc.) so they don't see additive loads the same way as much of the vintage gear does.
The downside is that since they are primarily aimed at home theater, they usually don't put much effort into the FM or Phono sections

So if you need to use those built-in functions, it's dicey. You can pretty easily work around the Phono issue with a modest cost external phono stage
Having said that, there are some very nice 5.1 and 7.1 receivers out there. And in your case I'd be leaning toward one. The reason I suggest this is that many of the better ones still had the vestiges of actually caring about FM and Phono
7.1 Example for reference only:
Brand Sony Model DA3100ES/B
Family Line Sony STR
Product Type Home Theater Receivers
MPN STRDA3100ES/B
UPC 27242687035
Key Features
Channels 7.1
Output Power 840 Watt
Amplifier Output Details 100 Watt - 4 Ohm - 20 - 20000 Hz - THD 0.09% - 1 channel(s) ( center ), 100 Watt - 4 Ohm - 20 - 20000 Hz - THD 0.09% - 2 channel(s) ( front ), 100 Watt - 4 Ohm - 20 - 20000 Hz - THD 0.09% - 2 channel(s) ( surround ), 100 Watt - 4 Ohm - 20 - 20000 Hz - THD 0.09% - 2 channel(s) ( surround back ), 120 Watt - 8 Ohm - 20 - 20000 Hz - THD 0.05% - 1 channel(s) ( center ), 120 Watt - 8 Ohm - 20 - 20000 Hz - THD 0.05% - 2 channel(s) ( front ), 120 Watt - 8 Ohm - 20 - 20000 Hz - THD 0.05% - 2 channel(s) ( surround ), 120 Watt - 8 Ohm - 20 - 20000 Hz - THD 0.05% - 2 channel(s) ( surround back )
Surround Sound Effects Digital Cinema Sound EX
Sound Output Type Surround Sound
HDMI No
Built-in Decoders DTS, DTS 96/24, DTS Neo:6, DTS-ES Discrete 6.1, DTS-ES Matrix 6.1, DTS-ES decoder, Dolby Digital Surround EX, Dolby Pro Logic IIx
Equalizer Included Yes
Equalizer Type Digital graphic
Receiver Tuner Type Digital
Receiver Tuner Bands AM/FM
Response Bandwidth 10 - 100000 Hz
Technical Features
Input Impedance 50 kOhm
Input Sensitivity 150 mV
Power Consumption Operational 450 Watt
Connectivity
Connectors Type 1 X AM Tuner Antenna input - rear, 1 X Component output - rear, 1 X Composite (Video) output - rear, 1 X Digital Optical input - front, 1 X Digital Optical output - rear, 1 X FM Tuner Antenna input - rear, 1 X Headphones output - front, 1 X Multichannel Analog Audio input - rear, 1 X Multichannel Analog Audio output - rear, 1 X RCA (2 Audio Channels) input - front, 1 X S-Video input - front, 2 X Component input - rear, 2 X Digital Coaxial input - rear, 3 X Analog Audio output - rear, 3 X RCA (2 Audio Channels) output - rear, 3 X S-Video output - rear, 4 X Analog Audio input - rear, 4 X Digital Optical input - rear, 4 X RCA (2 Audio Channels) input - rear, 4 X S-Video input - rear
Coaxial Digital Input Yes
Optical Digital Input Yes
Optical Digital Output Yes
Headphone Jack Yes
Miscellaneous
Color Black
Remote Control Type Universal remote control
Built-in Display Type Fluorescent
Bass Control Yes
Dimensions
Height 6.89 in.
Width 16.93 in.
Weight 46.3 lb.
I am not suggesting you get one of these as the sound may be a bit dry and analytical for you. What I'm trying to show is that these types of machines are quite comfortable with multiple speakers. You just forget all the bells and whistles. Configure for 2-channel and flip on speakers A+B
You'll need to audition what sounds best to you.