I am also on the same route. I gave my older PC to my kids to play with, but the original Dual core was kind of weak for that. (not to mention the original 667MHz RAMs, LOL)
I just recently upgraded from the original 2.4GHz Dual core to X3220 (I could not buy x3230). And loaded 4GB of 800MHz RAM (I know it can manage 8GB, despite Dell statement, but has a 32bit Win7 yet). It has a HD6570 low wattage GPU.
Already has a 240GB SSD and a 2.5" 320GB HDD inside to have a quicker system.
What I also found, that the stock cooling is not able to manage the 100W thermal power of this server CPU.
It is OK till 65-70W, but not further. Some ppl also highlighed some design issues with the cooler (airflow vs metal grill locations), I also followed up with some thicker rubbers on the plastic housing (it improved the situation a little).
The heat sensor applied directly on the metal grills, so when the grill temp goes up, the fan follows it at once.
Very hard to swap the fan, as it has Dell special connecttor, and hard to get an adaptor too (and you loose the fan control with the available one)
Still After 1 hours of gameplay (Terraria, Heartstone, etc), the CPU went up from 60-70°C to 85-90°C, then it started to stutter, and logically shut down I added new thermal paste (certainly), but it just extended the switch off time to 1.5 - 2 hours. Opening the side panel helps a little, but not too much.
What I found that the HDD plastic mount at the middle works as a blocker for the airflow, despite it has an extra fan.
Also, worth to mention, that the two 2.5" HDDs are in a small plastic bracket, fits into the size of a 3.5" HDD (the HDD bracket designed for)
So here came the idea: the front memory card reader is the size of a floppy drive (3.5"), and has those special positioning screws. Does it fit to the 3.5" plastic bracket for the 2.5" HDDs? YES. It has exactly at the same position holes you can use.
Still, because of the PSU, motherboard connector and the second RAM, has issues.
If you check the DELL memory card reader it has a strange because of the very same reason.
I picked up my Dremel device, and cut down the end of the plastic bracket.
And here we go: the SSD and the HDD took the place of the original memory card reader.
I took out the HDD bracket completely. It has TWO benefits:
a) much better airflow. The CPU temp decreased by ~10°C. Not reached 90°C yet (80-82°C only)
Still not perfect, but much better
b) Now I have space to add a stronger DUAL slot Low profile card, if it does NOT utilize double wide metal rear bracker.
Gigabyte, Zotac have double wide metal rear panel, but
-MSI Radeon RX 550 LP 4GB GDDR5 128bit PCIe (RX 550 4GT LP OC) seems OK
It is approx. 5x faster than my HD6570, and 50% faster than my Geforce 1030 in the other SFF Lenovo machine (I think the 1030 GDDR5 is currently fastest low profile and single slot VGA available, except one Chinese 1050 one, not available and very very noisy)
-Some 1050 or 1050 Ti seems have similar layout, or can remove the rear panel
I still install the DVD writer, but not connected (yet) because there is only 2 SATA ports on the Mobo.
Now I have enough space for a SATA card and the cables.
So back to the original post:
After removing the hdd bracket, maybe there will be enough space to install a new cooler to.
It requires still some investigation, as XPS210 has a BTX mobo, not an ATX one and need to check out the fixation points.
I found this cooler may fit into the housing, and may keep the original fan too.
ARCTIC Freezer 11 LP
It has a 92mm diameter fan, planned for max 100W, but the original fan's horizontal flow may add to the cooling factor.
Based on my quick "virtual" measurement, the 92mm fan may JUST not collide with the double slot wide
Or maybe this?