I have two SE/30 and recently equipped both of them with 64 MB from this source: https://www.amazon.com/-/de/gp/product/B00FAYV3NO
I found the price reasonable and with more than 32 MB you can add a nice ram disk, so I can recommend the 64 MB.
Boot time has increased by a few seconds but not dramatically. As I found out in another thread here the large ram increases boot time _before_ the happy mac. The Mac still boots up with 4x16 MB on bank A but it can only make use of more than 8 MB with mode32 installed. When it comes to large amounts of ram the Rom Initiator would only be needed for the latest APPLE UNIX A/UX 3.1.1, which needs a 32 bit clean rom. Otherwise it is not necessary.
Before connecting up the KVM mentioned in the companion thread, I had a Dr Bott DVI/USB KVM connected to 3xG5s and 1x MacPro 2008 and a 23" Cinema Display. The KVM worked splendidly, allowing recognition of the proper screen resolution and so on. However, the thing would randomly switch to the Mac Pro, even when the latter was asleep and during use of one of the G5s. I'd say this was round about once an hour.
Fault in the KVM or something that the Mac Pro itself is doing in the peculiar semi-wake-ups that later iterations of OSX is given to?