K2 nr. 3818:

Including SSB, DSP, antenna tuner, 160mtr and 2e RX input.

A second RX input is a must. Without a second RX input, a transceiver is useless for 160mtr and very often for 80mtrs.

In the area were I live, with a high noise level at the low bands, the use of a low noise RX antenna for 80/160 mtrs is a must. Therefore I use a two band 'receive only' coaxloop in the back of my garden. A good low noise receive antenne used by your oppenent station is better than a 1KW amplifier used by you. Sometimes I can receive DX stations. Twice I made a 160mtr QSO with a DX station, a VE and 4X with QRP 5 watts output in CW. Since I purchased the K3 the K2 is maily used for holiday operations. My opinion is that for portable operations, traveling with a tent an portable antenna and a morse code key, you can not have a better transceiver then the K2. Low power consumption, light, small and rubust enough.  It's receiver is able to pick weak (QRP) stations out of the noise. I found that I was able to hear weak stations that other big guys could not hear. More than once, especially during contest situations, I noticed this. The K2 gives four bandwitdhs for CW and four for SSB. My smallest CW bandwidth nowadays is 100Hz, the widest 700Hz. For SSB I use 2.2 and 1.8KHz, the other two filter setting for SSB are used with a shifted pitch to copy very difficult and distorted stations.
This K2 filter measurements differ a bit from the current situation, but can be used as a reference.
Once, on a bad day, accidentally I connected the output of my homemade 160 Watt amplifier to the second RX input of the K2.  (Yes sometimes I do QRO see this link) The penalty was a shorted C114 in the K2, and DC voltage at the antenna terminal.
Easy to fix, and as far as I know, no further damage.

K3 nr. 1792:

Including, antenna tuner, 100W PA, KBPF3, KXV3A, K144XV, filters FM, AM, 2.7KHz and 400Hz CW.
I am doubting to buy an even narrower filter for PSK31 (can be very crowded there).
Realy powerful are the online free firmware upgrades, the analog DSP bandwidth control with automatic roofing filter switching. The K3 has many input/output possibilities for transverters etc. I use the K3 together with the LP-PAN panadaptor and a Dell-D630 laptop.

The backside of the K3, plenty of interfacing with my other projects.